I don't think many people I know would abandon family, friends, language, and culture to move to a different country unless the incentive was very high. Moving to the USA is also quite hard and the rhetoric around it isn't great so even a double or triple salary (which I've heard is the norm in some industries eg. software) isn't particularly tempting.

I doubt Germany, France, Austria etc. would see much significant drain. Poorer countries (eg Poland) have been already hit quite hard and might be impacted a lot more by this though.