For example, if the loan agreement specifically allows for the lender to repossess the car even if it is in another country, then the lender may be able to do so. Additionally, if the car is in a country that has a treaty with the United States that allows for the enforcement of foreign judgments, then the lender may be able to obtain a judgment in the United States and then use that judgment to repossess the car in the other country.
As a general rule, the best way to try and avoid repossession of your car is to keep it registered and insured in the United States, and if you do take it into another country, make sure that you have a valid import permit and that you are aware of the local laws regarding vehicle ownership and repossession.
Ultimately, the best course of action if you are concerned about your car being repossessed is to speak with an experienced attorney who can advise you on your specific situation.