Even without the US, the EU combined forces are More than enough to deal with Putin; especially now that it’s become startling clear that the emperor has had no clothes and his own strength was largely fiction.
That being said, they would have to be much more careful regarding China supporting Putin.
But also, as someone already mentioned, Trump is a bloviating idiot. The US isn’t going to give up the convenience of having strategic military bases around the world; there’s no way the pentagon and cia would never allow it. They’d outright Kennedy the idiot if it came to that.