Will American high schools recognize a foreign MA?
The answer to this will vary, depending on location. It might even be so local as to be determined by the local school district, though state level regulations most likely apply. But, I would think that you can make the case that, for some programs, the MA is just as valid, if not more so, than the US "equivalent". Certainly EU degrees are high quality. 

But, the educational regulations of the various states are probably available online, or you could send a letter to the highest level administrator in any state and get back the correct answer for that state. 

And I'm assuming that the MA is relevant to what you would be teaching. 

Private schools, of course, have their own compensation plans. For that, you make your case individually. 

But, for example, the New York State regulations are available online.