I'm a Brit who's lived in America for ~8.5 years. There are plenty of differences in language usage that I've observed, but this isn't one of them. Curious to know what they meant by this.

British English tends to have extra (read: nascent) u's in it after o's, but "should" is spelled the same in British and American English.

Example -

British have colourful neighbours.

Americans have colorful neighbors.