My guess is that there is some tension in the voting population between wanting police to use this tech to solve crimes, and fear that a continent-wide database

My guess is that there is some tension in the voting population between wanting police to use this tech to solve crimes, and fear that a continent-wide database will enable surveillance abuses. A federated solution might reduce the abuse potential. But more cynically, it allows for the effective creation of a continent-wide database while reassuring voters that there is no continent-wide database.