I think you're vastly overstating the differences that exist in French. It's mostly accents with a few distinct words/expressions. The grammar, spelling, syntax

I think you're vastly overstating the differences that exist in French. It's mostly accents with a few distinct words/expressions. The grammar, spelling, syntax and everything else is the same. Sure, someone with a strong uncommon accent can take some effort to understand ("can't even understand" is a clear exaggeration except in the more egregious cases), but the language underneath is the same. French is very standardised, and "international French" is spoken by everyone. That description would fit something like German much better.