NATO already is mostly EU + US and then only Canada, UK, Turkey and some smaller ones which all are (politically) very close to the EU (much closer than to the US at least).
Would technically have to be a new one, NATO wasn’t designed to handle this sort of scenario. Of course New NATO would be an America-free roughly equivalent, with some different governance to prevent things like a single county impeding something everyone else wants.
It would be the end of NATO as it stands, there’s no reason the remaining countries couldn’t continue the alliance or start a new one.
NATO already is mostly EU + US and then only Canada, UK, Turkey and some smaller ones which all are (politically) very close to the EU (much closer than to the US at least).
Would technically have to be a new one, NATO wasn’t designed to handle this sort of scenario. Of course New NATO would be an America-free roughly equivalent, with some different governance to prevent things like a single county impeding something everyone else wants.