because we have alot of money in debt
No because our economies and goals are completely different. Havent you learned from the Euro that different countries in different financial states should not share a currency?
Like the guy above me said, look at Greece and the Euro to see what happens when multiple countries adopt the same currency. The US's, Canada's, and Mexico's goals and policies are too different to tie together their economies like that.
If one currency collapses we will still have other ones too depend on. If we only have one currency and it collapses we are screwed!
Not unless they (Mexico and Canada) drop their current governments and are added as U.S. territories (states).
Mexico will really F up our currency...