I'm curious about the thought process behind this as well. It's not like those countries don't have their own historical moments to pay attention to, let alone ones from other countries.
If in the US, the independence day of another unrelated country is celebrated or is a big deal, perhaps then I would wonder if it's the same in other countries. But I'm pretty sure that's not the case, so yeah.
Cinco de Mayo is widely celebrated in the USA and it is to commemorate Mexico winning a battle against France. Several Americans celebrate St. Patrick's Day, which is about the spread of Christianity to Ireland.