Francisco, I have two comments to make.
1. I know a number of non-Mexicans have, indeed, contracted covid; I also know of many Mexicans who have as well.
2. It seems you may be forgetting the bus-loads of people who poured into La Manz over the holiday. Canadians must be double-vaxxed in order to board an airplane (don't know about USians) and I seriously doubt there's any such requirement for boarding a bus in Mexico.

I implore you to not be too hasty in levelling blame.