Water usage is probably my biggest. Living in a high desert, my wife and MIL see no problem with filling one side of the sink with hot soapy water to wash a few dishes because “that’s just how I’ve always done it”, to watering the grass and plants for hours. All of this makes me mental.
When I was driving in Mexico, I learned this is possible! They’re very consistent with this.
California (not sure about other US states) on the other hand … people will purposely drive in the left lane, block traffic, and then get mad at you when you pass them on the right.