They also try to drive to canada with their guns, and believe they can't be "foreigners" because they're american. 30% of americans are functionally illiterate, no surprise really.
Embarrassing, but the statistic cited there is 6 cases in 2017 for a single crossing point, looks like there are ~1.5M visits a year[1] so I would imagine even if we're talking hundreds of cases (generous), still not too common?
US currency is accepted in a surprisingly large number of countries abroad. Just not in Europe proper. US dollars are even accepted in some European sovereign territories outside of Europe.
It is very convenient for Americans. Depending on the parts of the world you've traveled it is easy to get the impression that the US dollar is a sort of universal currency.
Which isn't to excuse the people in your story. It is pretty easy to find out if US currency works where you are traveling.
I've seen plenty of waiters, taxi drivers, etc., be quite happy to receive tips in USD in many countries where USD is not the official currency. In fact, I can't think of a single time when I've seen such a tip be rejected because of its currency.
That's quite different from trying to pay a bill (invoice) in USD in those countries.
No one expected anything and there wasn't any weirdness in getting a tip in your national currency. It's just that people happily accepted strong/popular foreign currency like the US dollar (I think that the Deutsche Mark was another option).
Sometimes you could even pay with it even if it wasn't officially accepted. Getting some money and then exchanging it yourself into the national currency (so that the accounting books are in order) is better than getting no money. And if it's a fuss, just charge a big extra, there's no need to make a big deal out of it.
https://immigration.ca/americans-frequently-caught-bringing-...