It’s not a crime, anymore than if a conservative governor cut ties with a bank over some liberal decision. And just like he can cut ties with a bank, congress can cut money to sanctuary cities.
It’s one thing to simply cut ties because of actions they are taking or might take. But when he makes a threat “if you do (or don’t do) X, I will do (or won’t do) Y”, that’s extortion. He’s made it vague enough that Mafia lawyers are taking notes, but it’s a direct threat.