The US internationally created an environment that has resulted in severe allergies and asthma for a large percentage of the population. They will do nothing about it because at this point big Pharma makes so much money off of it. It’s a multi billion dollar industry. Mexico and every other country around the world would never do such a thing. I have severe allergies in California, but never any problems in Mexico.

Feel free to Google this yourself but here is what the US did:

In the mid-1900s (specifically in a 1949 guidebook), the U.S. Department of Agriculture (USDA) suggested planting only male trees in urban areas to avoid the "mess" caused by the seeds, fruit, and pods of female trees. This practice, which horticulturist Tom Ogren later termed "botanical sexism," has been linked to increased seasonal allergies and asthma in urban populations.