Tires, tires tires. Now days, pretty much all tire sizes are available south of the US border. Didn't use to be. We ended up putting all new wheels on our Class C so we could get tires that were available here, then carrying two spares.
Homework, homework homework. Check out everything and prepare for it all, and not need any of it. THAT makes a perfect trip!
If you have a problem, and you will, just take it as it comes, consider it part of the adventure and move on.
We now live in Mexico, and even today, while renewing our vehicle registration, it's all an adventure! Easy, but oh so different.