That is not entirely true. Most countries accept STCW compliant CoC from other countries on a reciprocal bases. There are also requirements for medical certificates, Sea Survival and Firefighting courses and all relevant additional courses commensuration with the type of ship, position and trade, which also has to be STCW compliant.
Of course there may be other obstacle. If you are talking about domestic trade there may be requirement for work permit, or eqv.
NOTE: GMDSS certificate from the US MAY not be accepted by other Maritime Authorities. The same MAY apply to other strictly domestic US qualification that is not STCW based.
BTW; GMDSS certificate from the Vatican State is accepted though.
So it is NOT the same restrictions for foreign mariners as on US registered ships in most other countries/registers.
PS> In Norway there is also a requirement to speak Norwegian for anybody serving on Norwegian vessels carrying passengers in domestic trade. (Don’t know if other countries have similar requirements)
Otherwise, basic English is required on NOR and NIS registered ships in any trade.
One suggestions, is to save your cash reserves, try to find supplemental work in any industry. The worse thing for you to do, is go to another country, blow through your reserves and be stuck in a foreign country during COVID. (that is a recipe for disaster) How old are you? Have you thought about military or police/fireman? Also, CBP is looking for Mariners as well. It may not be your career choice, but it definitely puts you back in the game.
Let’s just say I’m too old for military, police, or fireman. I do not have reasonable access to any other jobs that I have an interest in. I do not have the experience or qualifications to compete in any other field. My only other background is on the railroad, another industry which is not only undergoing layoffs due to the pandemic, but also serious structural changes.