Cool story! But you might be surprised at how diverse language is in the United States. There are almost 400 million of us, and while we don't have as many distinct regional differences as exist in the British isles, our vocabularies can still vary enormously from region to region.

In the part of the United States where I live now, I wouldn't hesitate to tell a bartender, "Hey, can I get another can, please?" If I happened to be drinking canned beer, which, lots of excellent craft beer is sold in cans these days unlike in my youth when canned beer was crap. Lol

The usage of "can" for toilets, by the way, at least where I live, is archaic and has almost entirely faded out of use. It was generally accepted slang a few decades ago, and I think it lives on in some bigger American cities, but I don't think I've heard it in the wild in at least a decade.

The same with "underpants." You hear it sometimes, but I would never say it. It feels archaic in my dialect and also infantilizing – like a word a mother might use for her very young child's undergarment.

We say "underwear" most commonly, and while technically that's a generic term for anything worn under the clothes, people usually mean what you mean when you say pants.

Otherwise, we'll use a more specific term like boxers or briefs, or a slang term like skivvies, although that's a little archaic now too.

And the catch is, all of this varies enormously from region to region.

Here's an example. I live in Michigan, and here flavored soda water like Coke is "pop." The word is also very popular in Ohio where I grew up and parts of Indiana and Illinois. It's practically universal. Every kid knows what pop means and wouldn't probably call it by anything else.

But outside of the region, the usage is practically unknown, and while many people might understand the meaning, a good number of people would not.

I'll never forget moving to Alabama when I was a kid, and asking for a pop and a woman staring at me like I was speaking of foreign language. 🤣

Dialect differences within the United States are fascinating, and so are differences between British dialects and American dialects. Very cool subject!