Yes. But the last 50 years or so specifically, the US has been built buy foreign brains. Prior to that it was a mix of American/foreign labor. The US has become a service economy (especially in technology, energy, and healthcare) and many of the people who built that will gladly be scooped away by foreign institutions that will still fund their work
The people who founded this country were all immigrants. The people who physically built it, grew the crops, and made products were all slaves. In the modern age, people doing lower end jobs tend to be immigrants. I’m not sure what point you’re trying to make. America has always been carried by immigrants. Not any more now than ever. Can you point to some specific moment in the last 50 years that caused immigrant contribution to our economy to change? Because it’s been just as high as ever.
What I’m saying is that, now more than ever, the American economy relies on highly skilled/educated immigrants to develop new technology, contribute research, etc. Those people are now finding that opportunities are rapidly drying up for them in the US and they have every ability to go find work elsewhere. That wasn’t so much the case when the US was more of a manufacturing/industrial economy and the immigrants were generally unskilled laborers. I’m really not sure what point you’re
trying to make here. Nowhere did I try to say that immigrants didn’t contribute to building the US and its industries. All I’m trying to say is that rather than America being built by tens of millions of laborers, there’s now a much smaller group of highly skilled immigrants who contribute so much to a more service/technology oriented economy. And when the opportunities that drew them here dry up, they’ll find ones in the places they’d rather actually be