Europe is an US ally today not because of the geography, but because of the Europeans. But the Europeans have mostly given up making babies and will in 1-2 generations be mostly replaced by more fertile Muslims hostile to the US.
For example the English population in the capital of the UK, has fallen below 50%. The English are already a ethnic minority in their own capital. It is just a matter of time when the people making decision about the UK nuke arsenal and military infrastructure are Muslims loyal not to the Queen but to Pakistan, Somalia or some other Jihadi US hating shithole.
It would be silly to declare a quickly dying/changing continent an perpetual ally and stop monitoring them just because they have been allies 20 years ago.