Sorry
I only know the basics of the US situation - enough knowledge to be dangerous;-) You will need to ask someone who actually understands the US implications.
What I can say is that I know that in the US many are based in one country living in another. I suspect this practice would be severely curtailed with onshoring - IRS might check who has residency, paying tax, who has a green card etc. Similar things will happen in EUR - so onshoring has its costs as well as its benefits.
Presumably an onshore company will have to conform with all local requirements. For example, in Australia long service leave will accrue (unfortunately not back dated;-). So look around at what are contractual rights as opposed to employment benefits. If it is an inalienable right to strike, have paternity leave etc then being in an onshore company should bestow those same rights. However, read carefully what you sign as you may waive your right to many benefits other US company employee's enjoy.