Brian -

They're not different languages at all. Just variations of the same language. Dialects. Certain words, phrases, and accents differ, but it's definitely the same language.

It's not like a Brit would travel to America and not be able to understand what was being said. In fact, most of the differences are so minor that it really doesn't matter much at all. I'm sure an American could adapt to British English very quickly.

That would be like saying people in Kansas and Nevada speak different languages. Incorrect.