Not really. Your first step should probably be to hire a private investigator to do an asset search for you.
Real property records in the United States are maintained on a county by county basis and there are roughly 3000 counties in the United States (in Louisiana, a county is called a "parish"). There is not even a centralized state level governmental database of real estate ownership. And, many smaller rural counties don't make their real property records available over the internet. Moreover, in New England, lots of key records are maintained at the town level (all property in New England is part of some New England town of which there would be many in each county, and county government mostly handles the court system rather than other rural services).
Also, contrary to the suggestion of BlueDogRanch in the comments, a Will would frequently not contain a list of the real estate owned by the decedent, although the lawyer who drafted the Will may have taken notes indicating the real property owned by that person at the time it was drawn up. More commonly, a Will will set forth a formula for dealing with property. And as you indicate in the comments, there may be no will to find in any case. You should also ask if there is a trust in place, however, as some people set up a trust and dispense with a will.
Businesses are usually registered with a state secretary of state. These records reveal a registered agent and sometimes managers or directors of businesses, but not the ownership of businesses. It is possible to set a business up so that it has no obvious ties to an individual. Searching by the decedent's business and home addresses and the names of spouses and business associates and lawyers for the decedent, can sometimes reveal businesses that don't have the decedent's name attached to them.
Another public database that can be searched (at a price and with some technical expertise) is the personal property lien database also known as a "UCC Search" for the Uniform Commercial Code that requires that personal property liens be disclosed in this central filing place.
Furthermore, there is no central registry of financial accounts.
Incidentally, there is also no central database of divorce records in the United States. The court clerk of each court with jurisdiction to grant a divorce maintains these records separately.
Keep in mind, however, that unless a divorce decree said otherwise, usually a man has no obligation to leave his children anything at his death as an inheritance if he has a Will in every U.S. jurisdiction (unlike many European inheritance laws that require that a parent make bequests of some amount to children in the absence of special circumstances).
Strategies for Asset Searches
A variety of approaches are available to locate assets, although some of these are less viable when there is a widow who is the executrix of the estate who is in control of the situation.
Ask for an inventory and accounting of the estate and any trusts.
Normally, the person who administers an estate must prepare an inventory of assets owned at death and an accounting of the disposition of assets at death. A copy of the Will must also be provided. You can also file a demand to receive notice of all proceedings in a probate estate. Often these documents only need to be provided upon a written request.
This is an incomplete record. It doesn't cover transfers by gift prior to death, nor does it cover assets that are in joint ownership with a right of survivorship, nor does it cover assets with a beneficiary designation or a transfer on death instruction.
If he had a trust and you had any interest in the trust, the trustee is obligated to provide inventory and accounting information and a copy of the pertinent portions of the trust to you upon request.
Ask if he filed any estate tax returns (Form 706) or gift tax returns (Form 709) during his life.
If he had an estate of about $5 million or more at his death, he would have had to file an estate tax return (Form 706), even if no estate tax was actually due. This is due nine months after the date of death.
Unlike a probate inventory, a Form 706 captures both assets that pass via a Will (called probate assets) and assets that pass by a joint ownership or beneficiary designation or trust (called non-probate assets).
If he made large gifts to anyone other than his spouse during life, they would have had to be reported on a gift tax return (Form 709). This is due on April 15, of the year following the year in which the gift is made unless an extension of time to file is obtained. This would reveal large transfers to trusts that he made during life.
If he was wealthy but got around having to file a Form 706 by making lots of big lifetime gifts, there would be filings of Form 709 that would disclose those gifts.
Review the decedent's personal financial records.
These are usually kept at a home or office. Statements and records for various investments are often kept there. Also, bank statements can often be clues that can reveal other assets. For example, usually collectible items like art or gold coins would be purchased with a credit card or checking account and the purchases could clue you into the need to look for those assets.
Of course, getting access to these records could be hard if you are not in control of the estate.
Determine if there is a safety deposit box or safe, and if so, review the contents.
Often deeds to real estate, certificates of title, stock certificates for closely held companies, coupon savings bonds, and other important documents are kept there. Loan application forms can also be a great resource as they require a full disclosure of assets and there is an incentive not to omit assets in filling one out.
Of course, getting access to this could be hard if you are not in control of the estate.
Collect the decedent's mail over the course of a year.
Almost all real estate gives rise to a property tax bill at least once a year and more often twice a year, and financial accounts issue statements at least once a year in most cases and often monthly or quarterly.
Of course, getting access to this could be hard if you are not in control of the estate.
Pull a credit report, then repeat about a year later.
Credit reports reveal who the decedent had accounts with, which can be a one stop shopping list for bank statements to obtain and review.
They also capture accounts that the decedent won't get in the mail because there is a bad address. By a year out from the date of death, any big business creditor that isn't sending mail (e.g. because the creditor is sending bills to an email address you aren't aware of or don't have access to) will show up as delinquent in a credit report.
Substantial credit is usually only granted to people with lots of wealth. If there is no debt or only little debt on a credit report, this tends to corroborate the idea that there is little wealth.
In particular, credit reports reveal outstanding real property mortgages and personal property secured loans with financial institutions that are outstanding, which can be used to locate assets.
You may need a private investigator's assistance to access credit records if you are not administering the estate.
Look at the decedent's most recent income tax return or two.
If the decedent didn't keep them, a transcript can be obtained from the IRS. Of course, getting access to this could be hard if you are not in control of the estate. But, you could always ask.
Investment income lines will reveal any financial accounts that generate interest or dividends or capital gains (although it won't capture "coupon bonds" that only generate income when redeemed, like U.S. savings bonds or no interest checking accounts or closely held C corporation stock that doesn't pay dividends).
There will be a "Schedule K" contribution to the tax return of income and expense items from any S-corporations and any closely held partnerships, LLCs or business trusts that had income or losses in that year.
Residential real estate will normally give rise to property tax and mortgage interest deductions (unless there is no mortgage or the mortgage is small, in which case the Standard Deduction for personal deductible expenses will be claimed).
Investment real estate may have generated rental income, depreciation deductions, and/or mortgage interest deductions (even if the decedent did not otherwise itemize deductions) and at a minimum there ought to be property tax payment deductions.
Contact the attorney who drafted the Will, if known.
While a Will rarely contains a detailed list of assets, the attorney drafting it usually prepares a list of the major assets that someone owned at the time it was drafted and keeps a set of those notes in the file. This may not be useful if the Will was drafted many decades ago (many people draft their first Will when they join the military or get married or first have kids and never change it). But, it may be helpful if it was drafted recently.
An attorney may decline to speak with you on the basis of attorney-client privilege, however, if there is an executrix in place already managing the estate.
Obviously, this doesn't work if he did no estate planning and plenty of people die without a will. Less than half of deaths even give rise to a probate proceeding at all, because lots of people die poor or don't have any probate assets at death.
Hire a private detective.
Private detectives live less glamorous lives than you'd think. One of the most common jobs that a private detective is hired to do is to locate assets for a creditor or for a probate estate. They have access to proprietary databases that are not available to the general public. But, they aren't cheap.
In your case, this may be the only really viable solution, and while they aren't cheap, they know what they are doing and would probably be more efficient and more complete in their search than you would be. You can learn a lot with a few thousand dollars.
Also, if the PI's investigation reveals substantial U.S. assets, you will probably be able to hire a lawyer who will accept payment when concealed assets are secured from the probate estate (perhaps with interest or on a contingent basis). So, hiring the PI is probably a higher priority than hiring the lawyer as a first step.
Hire a lawyer
A lawyer can efficiently demand information from the widow who is the executrix through formal channels.
More importantly, if your PI discovers that assets have been concealed, your lawyer could arrange to have the widow removed from the job of administering the estate and have one of your family members, or a neutral third party professional, appointed to administer the estate correctly. And, an estate administrator can use the tools discussed above to do a more complete and accurate search for assets than a PI could.