Uncle Cecil addressed this at: http://www.straightdope.com/classics/a5_059.html
Damn, and here I thought I could get to be all cocky and say “Looky here, Cecil did a column on this and it’s on the front page of the site today!” But noooo, you just had to come in and spoil it, you Esquire you.
Anyway, the US has the vast majority of tornadoes, but not all.
I sold my soul to Satan for a dollar. I got it in the mail.