Regarding travel, it isn't typical for US defaultism for Americans traveling abroad. However, not typical doesn't mean that it doesn't happen in some forms.

Regarding currency, a lot of countries and regions will take American currency. Some smaller Caribbean countries peg their dollars to the American dollar 1:1. Some touristy regions around the world will also take American currency, usually at inflated prices. Or, you may have a tourist who has run out of the local currency and only has American cash on hand. It isn't typical, but it likely happens and everyone remembers the few idiots who don't know that France uses Euros.

Regarding language, it can be stressful for some to be in an area where people are speaking in a language you don't understand, especially if you are used to people only speaking your language. Yelling "Speak English" could be someone having a panic attack or just expressing frustration that they can't interact with society like they could at home. Sure, there is likely some racism and ignorance wrapped up in that. However, I'm providing an explanation, not an excuse.