Fellow Latin Americans/Africans/Asians/Oceanians, what is something that Americans and/or Europeans have/do that makes no sense to you?

Milk in tea is only universal for English/Irish breakfast tea(idk how popular they are outside wester Europe but in England/Ireland if someon says tea they mean breakfast tea and will specify otherwise)for something like chai or eal grey 1/3~(anicdotally) of people who drink it wouldn't have mik, and the milk isn't hot it's normally fridge-cold to room-temp the tea bag is steeped in just water, the point is to sweeten the rea and cool it down

If it's milk being added to tea that surprises you, it is a regular drink in south and south-east asia, not unique to the west. The latter especially has this drink called "teh tarik" that uses condensed milk and is awesome but diabetes-inducingly sweet.

American. I normally drink my tea black, but milk is nice with earl grey on occasion.

And typically, the milk isn't hot. You pour it in already steeped tea, like you would if you drank coffee with cream.

That said, I do occasionally steep my earl grey entirely in steamed milk and add a little vanilla and it's just a nice treat. But I'm not looking for a bitter flavor at that point either.

Honestly, I thought putting milk & sugar in your tea was bonkers until I tried it from my British friends. It works with traditional English teas, but not really with American/orange pekoe teas.

There are some English teas that are so bitter that they need sugar in order to be palatable.

You're posting from an Indonesian server, so this is a particularly hilarious take.