Under U.S. law, a U.S. court can assert jurisdiction sufficient to enter a binding judgment (called "long arm personal jurisdiction") if the events giving rise to the lawsuit took place in the state where the state or federal court in which the suit is brought is located.
Generally speaking, modern U.S. law allows the service of the summons and complaint that gives the court jurisdiction over the defendant if the events giving rise to the suit took place in the state, to be served anywhere in the world (or even in outer space, for that matter).
But, the practical reality is that serving someone with process from a U.S. court in another country would be difficult and expensive, and enforcing the judgment if you win could likewise be difficult.
There are also a couple of other problems specific to small claims court:
Many small claims courts do not have the full jurisdiction that the U.S. Constitution allows them to have by virtue of the statutes that authorize them and their contemplation that proceedings take place predominantly or entirely in person. It isn't uncommon for the statute authorizing a small claims court to limit its jurisdiction to defendants that live in the same county.
Most small claims courts are only allowed to enter money judgments subject to some very narrow and idiosyncratic exceptions. Most small claims courts do not have jurisdiction to order specific performance of a contract to sell a car, even though they could award money damages for breaching the contract to sell the car if those money damage could be demonstrated convincingly.
These barriers particular to small claims court could be solved by filing suit in another state court that has broader jurisdiction. (The federal courts would probably not have jurisdiction over this case even if there was "diversity of citizenship" between the parties because the amount in controversy would probably be less than $75,000 unless it was a very fancy car indeed to be worth that much used.)
Different consideration would apply if these facts and circumstances arose outside the United States, depending upon the jurisdiction in question.