I do not believe the US will invade, at least not for quite a while. It would be economic suicide and is very unpopular even amongst Trump's own voter base. Will he in the future? Maybe, and we absolutely should plan for that. Canada needs a proper military and our forces can no longer exist as just an arm of the US military.
I think what happens next will largely depend on our government(s) going forward. Trump's temper, imperial ambitions, greed, and pride all ride on a constant knife-edge and dealing with him requires a skilled and smooth hand. We can further our ties with the US and essentially become a vassal territory, or we can seek new allies and deals elsewhere which seems to be the route we are taking at present.
Canadians need to get used to the new reality that we now share a border with a fascist dictatorship lead by a screaming near-80 year old toddler and an army of yes men. I think we are going to end up a lot like Finland in that living under the constant threat of invasion is an aspect of daily life. The bear hasn't struck yet but one day it will and every person needs to be ready and know how to respond.
Securing our democracy and economy is paramount. The Americans will be attacking our elections, our media, and our protected industries. We have been doing a good job at getting people to stop buying US products but we need to get them off American social media and news sites too - it is literally a matter of national security.