Centralized messaging services won't last long, their capture is sadly inevitable. In the long run, only self-hosted/decentralized protocols can resist what's coming.
In the meantime though, Signal specifically should not do something stupid like blocking the EU, which is basically surrender. They are a non-profit headquartered in the US, so there are zero business risks to non-compliance - nothing in the EU to fine or seize. And the EU has no jurisdiction over servers in the US, all they can do is build their own Great Firewall. (However, they might pressure AWS to deplatform Signal - hopefully the team is prepared for the possibility that self-hosting will be necessary soon.)
In the meantime though, Signal specifically should not do something stupid like blocking the EU, which is basically surrender. They are a non-profit headquartered in the US, so there are zero business risks to non-compliance - nothing in the EU to fine or seize. And the EU has no jurisdiction over servers in the US, all they can do is build their own Great Firewall. (However, they might pressure AWS to deplatform Signal - hopefully the team is prepared for the possibility that self-hosting will be necessary soon.)