I agree with this analysis; it would be hard for American scientists with spouses and children to relocate. However, there’s another thing to consider: the amount of researchers from grad students all the way to tenured professors and senior industry researchers who are not American citizens who moved to America for their careers.
The following is anecdotal and I don’t have any statistics. When I was a PhD student at UC Santa Cruz, roughly half of my classmates were foreigners, many from mainland China and India, but also from Iran, South Korea, Greece, Uruguay, and Mexico, to name a few. My first advisor was a German who became a naturalized American citizen, and while roughly half of my professors were native-born Americans, I also had professors from China, Ireland, Greece, Singapore, and Argentina. During my time in industry in Silicon Valley as a researcher, I’ve worked with many people who grew up abroad and moved to the United States for grad school.
The biggest issue I see with a brain drain in America isn’t necessarily Americans going abroad, since it would be a major sacrifice giving up family and friends to move to a place with an unfamiliar language and culture. The problem I see is when immigrants to America who have already made those sacrifices end up leaving America, either to return to their countries of origin or to different countries. If a significant number of immigrant scientists leave America, this will be a tremendous blow to American science, and this may also be a boon to countries that are willing and able to hire these talented people.
China, for example, has the money to fund science at levels competitive with the United States. I don’t foresee a lot of Americans moving to China, partly due to the language barrier, and also partly due to China’s political system. However, what if Chinese researchers in the United States return to China en masse? This is not good for us, though it would be great for China.
These are scary times in America.