I’ve seen posts online or memes about it, mainly discussing American people who think the internet as a whole is US-centric despite the topic at hand taking place in another country (nothing to do with America), for example: someone wrote the date format as 30/10/2020 (using the EU format) but some American was like “THE CORRECT WAY IS 10/30/2020” when they fail to realize that user is not American at all.
Is US defaultism real when they travel abroad? They assume the $ is legal tender worldwide in countries where their own currency is used more (the only thing that’ll work is exchanging it but not for direct transactions). I’ve heard an American woman went on a tirade whilst in France as the cashier refused a $20 bill when the prices are in EUROS (WTF?) or being like “SPEAK ENGLISH!” in non-English speaking countries.
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.