Unless something radical happens then NATO with the US is probably coming to an end, for now.
The name might continue or it may be reformed as a new organisation. North Sea European Alliance?
The UK and France will provide a joint nuclear counterforce. Defence spending will need to increase in Europe to compensate for the US no longer being involved. More Taxes.
The ongoing Trade Wars won't help at all. For anyone. Less Trade and Less Revenue.
If UK/US intelligence cooperation is reduced or abandoned that will be a huge issue going forward. For both parties. Less knowledge and information.
Europe will get involved in Ukraine more directly. More ramifications.