This is extremely good for Europe (as people will go there instead of to the US).

So they certainly won't

EU (and Canada and Australia) can capitalize by

1. Actively poaching US employers to quickly setup shop in EU

2. Give visas to tech workers

Outcome? More business activity in the EU, more tech industry and instant boosting of GDP coming out of covid.

Why would the EU complain about Trump ending the brain drain?

It's a good decision by Trump. It benefits American workers and non-American nations. Win/win.

The losers are the Gates and Bezos who are already extremely wealthy. I will find have to find a source but I think there is a gap between the share of profits captured by IT workers vs banking workers in the US, and those are industries with equivalent levels of workforce education and capital intensity.