One of the biggest lies in cultural thinking is that countries like Ireland and the UK are "culturally close" to the USA. Sure they are close-er than say Italy or Japan, but anyone who thinks "close" means "similar enough that it doesn't matter" is in for a rude awakening.

In reality there are incredibly large gaps around even the most basic things like the meaning of words. As a very basic example: the meaning of the word "interesting" differs radically between cultures. Most US employees would think the boss is indeed interested when they describe an idea as "interesting" and may even bring it up again at some later date after more research. Meanwhile, someone from the UK means that it's the dumbest thing they've ever heard and they will be incredibly miffed if it is ever brought up again.

I've certainly experienced US-made software that was close to useless in the UK, demanding dates in some absurd middle-out format and expecting everyone to know what a "401k" was with no explanation, along with more minor bits of polish like saying "pound" but meaning a completely different symbol.

Hah, good point. If anything, software handling that kind of data might be better is smaller countries that need at international audience from the get-go!