If I had to guess, it's because in neither of those locations did people lose rights that they had previously been granted. This is a substantive shift in peoples' bodily autonomy. If you don't want theocratic fascists inspecting your body, all of a sudden you have to uproot.
Probably because you can move between U.S. states without a visa, which is required to permanently work in another country. I feel like Google could do something similar between it's different offices in the Schengen area, but moving from Ireland to Mexico or from USA to Italy is going to require a lot more work and paperwork than most people are willing to put in, especially if there's a simpler option already available.