How much does—or did, recently—the United States federal government invest in scientists in the USA? Is it ~$70 billion a year? [0]
Europe can achieve America's (past) results when Europe starts talking with money. Science migration has historically gone in one direction across the Atlantic, and it is 100% about who pays better. The EU isn't remotely close to funding its own scientists properly—let alone attract new ones from abroad!
If European science benefits from the ongoing government implosion in the USA, that'd be entirely due to the US' unforced error. EU's politicians deserve no credit.
[0] https://en.wikipedia.org/wiki/Science_policy_of_the_United_S... ("Science policy of the United States")