I understand what you're saying, but there is no way you're going to be able to tell the difference on an internet forum......Any knowledge of this situation? (Not guesses, nor opinions, just first-hand knowledge - PLEASE)
I have found this to be true in a lot of cases, as even American owners will not hire American citizens as crew because of the litigiousness of our society. We have been aboard several large American owned (not flagged) yachts without one single American on the crew.On the flip side, I'm told that many US vessel owners are motivated, in part, to flag their vessel in a foreign country, or a non-state US possession, because it makes it easier to hire a foreign crew. Not the OP's question, of course, but I find that interesting. I can't quote the law, just something I've heard.
To the OP, you're getting about the best you can expect from asking a bunch of strangers at the bar. No one is trying to be rude or critical. It would be a great contribution to the community, if you let us know what you learn in your pursuit. I'm sure others are interested. Good luck.
The above is what I've found so far in researching this on various websites that seem to be authoritative.My search on the Internet indicates a) the Schengen visa is not required for US passport holders, and b) the Schengen visa is not a work permit, though it permits business trips.
Further research indicates that to work in another country requires a specific country issue a specific work permit to work solely in that specific country.
I understand it's a touch more complicated than that. I think what you pay depends on a number of factors, such as whether you are working for a foreign affiliate of a US employer or for a foreign employer, or even whether you're a government employee. Whether you still reside in the US and are working overseas, or reside overseas too. Then, I understand income tax is an entirely different beast from medicare and social security. Gives me a headache.US citizens pay taxes regardless of where the income is earned.