They said specifically in the bid that they would be able to 'beat the heat with air-conditioned stadiums'. I don't understand why the USA is not a permanment backup bid, they already have MASSIVE stadiums in place anyway.
And nobody cares about the North American leagues, outside of North America. Imagine how pissy the english- no, Europe in general(minus Russia and Scandinavia) if they decided to postpone the leagues for the World Cup. There would be RIOTS in the home of football.