Why do you have to type in 'google.mail.com' instead of 'gmail.com' when outside of the US?

I lived in Germany for 5 years and recently moved back to the US. While I was there typing in 'gmail.com' would result in an disclaimer stating that google could 'not provide access to the gmail.com web address outside of the US or link to it' and that I needed to instead type in 'google.mail.com'. What could possibly make it so that the gmail URL isn't allowed outside the US? It's not a problem, I'm just wondering.
Why do you have to type in 'google.mail.com' instead of 'gmail.com' when outside of the US?
Because other companies trademarked the name gmail before Google in other countries.