There are several differences, right? Both Americans and Canadians primarily speak English but we use different vernacular.
We have different governments, even though we’re both democracies. The U.S. has a president, while Canada is run by a Prime Minister.
If you’re from either Canada or the United States, you know the many things that make us different despite someone on the other side of the world possibly thinking just because both nations speak the same language and are located right on top of each other.
Same thing with North and South Korea, except they have many, many more.