A cultural problem? No, it's an economic/policy problem. PhDs are effectively being compensated with green cards instead of money. This compensation package is much more attractive to foreign students for obvious reasons.

I'll never forget the day in lab meeting when it came out that I was a US citizen. I thought my accent and appearance would have made it obvious, but evidently my coworkers had assumed otherwise, and the response was an astonished "Then what the hell are you still doing in academia?" followed by looks of pity when I admitted to loving research. This was a biomedical lab at Carnegie Mellon about a decade ago and I was the only one doing ML work, so their astonishment was in part due to an underestimation of the market value of my degree, but on the other hand their intuition was likely accurate with regard to the STEM PhD market outside of AI.

Those PhDs are worth $pittance + green card, but not worth $pittance.