You're right that Mexico has a better climate for growing fresh produce, it's where Canada also gets a large portion of out-of-season produce from as well.

If I understand correctly, the reason as to why there is a significant spike in food contamination & infection/illness in the US is due largely to the rollback of funding & legislation by the current administration, which makes it more difficult for those in the food inspection & quality control sectors to work effectively for consumers.

Another workaround could be to buy frozen produce, as there doesn't seem to be a lot of news about contaminated frozen fruit & veg. Hopefully, at least!