Both have fairly similar origins. Mexico and the US were new, large, resource rich, sparsely populated countries, whose governmental institutions were created in the industrial revolution. I think it would not be much of a stretch of the imagination that had events gone slightly differently, we could be living in a world where Mexico would be on par with the US, and maybe even supplanting the US as the world's dominant power.

So, what is the reason for this current disparity? Was the Mexican American war much more influential than many people give it credit, was America just blessed in some way that I am not seeing, or is it something else?

edit: Wow. Apparently I have hit a really touchy subject. Every time I refresh my browser it will fluctuate between +5 and 0. Didn't mean to offend anyone, I am just interested in the subject.