I think it will not change anything to be honest. I work for a relatively large US company we have offices in CA, VA, NC, Ireland, Germany, India. If it becomes harder to higher in US
they will just grow teams in other offices.
But not every organization is internationally distributed like that. If physical location of employee really didn't matter, then your org would have most of its IT staff in India, because the labor rates are lower and that's the largest pool of English-speaking IT talent.
I agree there is some fluidity to IT labor, but there is a limit to it also.
Besides, the stated on-paper purpose of H-1B visas is to fill (alleged) skills shortages. After the dot-com crash there was a big surplus of labor in the area, yet us citizens were competing with H-1B's still. The stated goal was missing the target during that time.
