People tend to see the US's isolationist moves as being Trump's doing, but he was elected in part to do so. If he were to resign or be impeached, it would be undemocratic for his replacement to abandon this direction. I doubt that Trump will resign or be impeached, and he might win a second term. How isolationist will the US get? Unknown, but for NATO members and other US allies, preparing alternative armaments production and defense alliances MUST be considered. If Europe pursues alternatives, Canada should join in. I don't suggest abandoning the US, but being unprepared would be dangerous for Canada and keeping a bridge open between the US and EU would be wise.