A B,

You make several juvenile assumptions here. 

While shared personal empathy and broad agreement on public policy obviously help the leaders of two nations navigate bilateral relation between those countries, unless one or both leaders goes out of the way to gratuitously foster disputes each will proceed to advance the interests of their country and both will proceed in a business-like way to that end.  I see no reason why the relations between Canada and the US (and by extension, between Trump and Trudeau) should be unduly strained.

Trump has many large issues unrelated to US-Canada relations to address (as does Trudeau) and neither will want to get bogged down in unnecessary US-Canada bilateral disputes.  The share market is important to both countries and neither will want to put this gratuitously at risk over personal differences.