It is not in the abstract a bad thing, and things like this are fairly inevitable under the circumstances. It's probably not a great thing for the US's foreign policy, and particularly trade policy (if you can call the current random flailing a policy) if the cause of it is treating the US as a common adversary, however.

On some level, Trump clearly understands that this sort of cooperation would be a problem for him (https://www.politico.eu/article/trump-threatens-eu-and-canad...), but I'm not sure if he understands that it is _inevitable_.

> If American policy is what keeps them apart, which I strongly doubt

No, it's not that. Current US policy is _driving them together_, however.