Something I find quite strange is how South American countries pervasively discourage people from flushing used toilet paper (instead preferring to have a little wastebasket to collect it and later throw it away in the trash). The usual account of the reason for this is that the plumbing can't handle it -- which you also hear about some old buildings in the U.S. OK, but this norm persists even in buildings that were…
(This is not intended as a criticism of Mexicans, merely a comment on the fact that just across the border such practices still remain very active. Unfortunately due to the clash of expected practices, their belief that it's necessary to avoid clogging plumbing, and the U.S. lack of such a practice meaning there isn't a wastebasket beside each toilet, it often leads to rather unhygienic restrooms. In some cases, stores compromise and put wastebaskets in as well so everyone is satisfied.)