It is also possible that most of the matches will be held in America and the remaining small or group matches may be held in other countries. The FIFA authorities can do something like that the final semi-final knockout stage matches will be held in America. Actually, it cannot be said right now, we hope to understand everything in the future.
Why possible, when all the stadiums are already known and most of them are in the US. I think when all the country teams will be knows, the drawing will be done so, that it will be convenient for countries to have games in specific countries. The South American countries will play in Mexico, European probably in US, African either in Mexico or Canada. And after prelims all the games probably be in US only.