Buying a used tire to carry as a spare?

While traveling the hinterlands of Canada, note that it's possible to go 200 odd miles without any towns, meaning services are few and far between. So, keep an eye out for road hazards. Miles of gravel instead of blacktop is possible. Depressions in the roads are common, and you hit one of those at 55 the compression can separate tread enough to cause a leak and blowout so drive conservatively. The other advice is in the northern part of Canada, the roads have hundreds of frost heaves crossing the road. Where the blacktop is pushed up and peaks. Hitting those at speed is dangerous. But the road service up there puts these little orange triangular flags on either side of the road shortly before the heave so you can slow down in time.

RV parks are usually a leisurely day's drive apart. You get in a big hurry, you'll likely not have a good time.

Have fun up there.