The US milirary will have hardcore maga cultists vs the “normal” conservatives + everyone else in the military that’s pro-constitution and they’ll fight each other. National Guards might also be join the fight. All Democratic governors will tell their national guard to disobey any trump orders and declare any of such orders unconstitutional, and they’ll be ordered to help the pro-consitution side. republican governors… that’ll depend. If they have a “Brad Raffensperger” type of governor, they’ll also tell their National Guard the same thing and fight for the pro-consitution side, but then you have those maga republican governors that’ll tell their national guard to help the maga side.

But it ultimately comes down to the people holding the guns and which orders they obey.

So… to re-iterate: there will be an internal conflict before Canada would ever see the invading US forces, and if the pro-constitution side wins, they use the 13th amendment to remove any congress people that supported the illegal invasion, then new elections are held (and for the senate, temporary appointments will happen if the state allows it, and they serve until the special election). There would probably be a huge overhaul of the country, and it will be like post- Civil War USA, but this is v2. This will be the second “Reconstruction”, hopefully it doesn’t fail again like the last time.