Oh you think that was bad? When I was that age my teachers were flagging to my parents that I kept switching between American and British spellings at random. Doing lots of programming in US English was causing my schoolwork to be frequently marked wrong (the teachers were fortunately quite forgiving about this type of mistake). It was just hard at that age to remember which of "color" and "colour" were correct in different contexts and ditto for a bunch of other words. Also for a brief period I thought the right way to write a zero was with a strikethrough because of the monospace fonts.
Other fun US/UK cultural issues: interview questions like "how many pingpong balls fit in a school bus". To Brits a school bus could be literally anything from a coach to a small vehicle, they aren't standardized like in the US. Even when you remember the big yellow buses from films, how big are they? If you never saw one in real life it's hard to imagine. Also it took a while before I figured out that "ping pong" meant table tennis. Fun times.
Other fun US/UK cultural issues: interview questions like "how many pingpong balls fit in a school bus". To Brits a school bus could be literally anything from a coach to a small vehicle, they aren't standardized like in the US. Even when you remember the big yellow buses from films, how big are they? If you never saw one in real life it's hard to imagine. Also it took a while before I figured out that "ping pong" meant table tennis. Fun times.