The US government is not required to publish a single list of "embargoed" countries, however defined. They are, however, required to publish the legal underpinnings of any restriction. This takes two forms. First, Congress must pass some law that enables the restriction. This page hosted by the Senate explains how to find such laws, however, it only goes back so far. You can find all of the US Code on the House US Code website. Usually, any change of sanctions don't require new legislation. The second set of publications are executive orders and executive-branch regulations, which are published in The Federal Register. For example, this is an executive order (February 21, 2022) regarding blocking of certain persons and transactions related to Russia's invasion of Ukraine. The Bureau of Industry and Security, Department of Commerce then published an implementation of that order, which is published in the Federal Register. The Office of Foreign Assets Control, Dep't of Treasury later published licenses related to this.
The obvious problem is that hundreds of pages of information are published in the Federal Register every day, so keeping up with the rules is challenging. A partial substitute would be to check the web page of each department that might be involved in promulgating such regulations. The Dept. of Treasury has pages on financial sanctions. One thing they provide is useful information about is list of countries that you need to worry about in terms of U.S. sanctions: there is no list. As they explain,
U.S. sanctions programs vary in scope.Some are broad-based and
oriented geographically (i.e. Cuba, Iran).Others are “targeted” (i.e.
counter-terrorism, counter-narcotics) and focus on specific
individuals and entities.These programs may encompass broad
prohibitions at the country level as well as targeted sanctions.Due to
the diversity among sanctions, we advise visiting the “Sanctions
Programs and Country Information” page for information on a specific
OFAC’s Specially Designated Nationals and Blocked Persons List (“SDN
List”) has approximately 6,300 names connected with sanctions targets.
OFAC also maintains other sanctions lists which have different
associated prohibitions. Many individuals and entities often move
internationally and end up in locations where they would be least
expected.Accordingly, U.S. persons are prohibited from dealing with
SDNs regardless of location and all SDN assets are blocked.Entities
that an SDN owns (defined as a direct or indirect ownership interest
of 50% or more) are also blocked, regardless of whether that entity is
separately named on the SDN List. Because OFAC's programs are dynamic,
it is very important to check OFAC's website regularly.Ensuring that
your sanctions lists are current and you have complete information
regarding the latest relevant program restrictions is both a best
practice and a critical part of your due diligence responsibility.
The Dep't of Commerce has a less-useful list, the entities list, and also a Trade Enforcement web page.
You should note that sanctions against the Central African Republic stem from Executive Order 13667 of May 12, 2014, but the Dept. of Treasury amended the regulations as of September 29, 2022 not in response to a new executive order. This is reflected on the Treasury Dep't web page on sanctions. It is unknown, and perhaps unknowable, whether the Dept. of Commerce will promulgate any foreign sanctions regulation that are not mirrored on the Treasury Dept. web page. In the case of the CAR sanctions, the executive order directed Treasury to write rules, though the Sec'y of State also received ordered (not related to financial sanctions).