I don't know what's the reason behind why Qatar wanted to host World Cup because it's probably not the money they are after because they are already petrol nation which economic doesn't need some more boost as with or without World Cup, their nation is already rich enough. And I doubt if they after the tourist because from my perspective, they aren't much of a tourist friendly nation.
Qatar has a lot of money, in fact, but a country does not live on money alone.
Qatar needs to create business relationships, get closer to the world and that's why they always host the biggest events in the world.
Football was just one of them, but every month there are big matches of great importance in different areas that take place in Qatar.
America is not so easy to travel - the visa issue is always a problem
on the other hand - Qatar is easiest to travel and they an amazing work in hosting the world cup - there is no doubt about it
I believe that the countries involved (mainly the United States) will make the requirements to obtain visas more flexible during the period in which the world cup matches will take place.
And I still believe that it is easier to travel and settle in American countries (besides being cheaper) than it was in Qatar.