The 'brain drain' (as you refer to it) stems from intelligent/motivated grads in the US for the last two decades (at least) pursuing more lucrative fields like finance and adtech (re: Google, Facebook). Or some pursue management route (attending big MBA schools and switching to management roles where they climb corporate ladder). In other words, there are not a lot of college/grad students who want to pursue traditional engineering routes in the US.
I myself was an electrical engineering (EE) major until I switched to computer science in my third (junior) year of college because like a friend of mine at the time told me, "<my name>, if you don't major in computer science, you will not be able to find a job easily after graduation". He was right. All of my former college friends in EE ended up pursuing programming jobs (a few of them now works for FAANG; I used to work for one but left a year ago due to RTO). That is why the US has no sufficient personnel to do traditional engineering jobs and we have shipped off a lot of those to foreign countries.
I myself was an electrical engineering (EE) major until I switched to computer science in my third (junior) year of college because like a friend of mine at the time told me, "<my name>, if you don't major in computer science, you will not be able to find a job easily after graduation". He was right. All of my former college friends in EE ended up pursuing programming jobs (a few of them now works for FAANG; I used to work for one but left a year ago due to RTO). That is why the US has no sufficient personnel to do traditional engineering jobs and we have shipped off a lot of those to foreign countries.