I've played Mexican Strats several times, and my local music shop just got a beautiful 3-tone sunburst american strat that I absolutely love. I would have to say the Mexi strat didn't feel half as good, but then again, it's half the price. Another thing, the sound. I've played both through relatively similar amps, and the Mexi strat just doesn't cut it. I prefer my Epiphone Les Paul by far. The American strat just felt right in my hands. (I'm pretty sure all you guys know what I mean) I think that you get what you pay for. If you have the money go for the American strat, because I don't really like the mexican strats. Despite what has been said about them having the same parts, I'm not exactly sure what it is that makes the American ones so much better, but they sound and feel 10x better than the Mexicans.

Btw, never take a salesman at a Guitar center's word, because they just wanna make money.