France cooperates more eagerly with Hitler - for example, they collapse faster, Hitler occupies less land, and there is less of a Free France movement. As thus, it is decided they should be punished after an Allied victory (I think there were various Allied politicians who wanted this to happen IOTL), and Britain takes all their colonial holdings, possibly with a few exceptions. That's millions of square kilometers right there just in French Africa (somewhere between 5-7 million if my estimates are correct).