The Americans are better, I've got a mex, and my mate has an american. His sounds better. I prefer the feel of mine, but that's only because I'm used to it. Mexican strats have lower quality everything.
You could upgrade bits of your mex...
You notice the pickups most, the americans have a much clearer tone, and pickups are easily replaced, so that's easy.
There's no need to replace the tuners unless your mex doesn't hold tune very well. If this is a problem, maybe replace the string tree with a better one before you shell out for tuners. Check the nut's well lubricated too.
The bridge parts make a reasonable difference too, and it's hard to replace them with american parts because the mexican guitars use metric measurements, and the american parts use imperial. Callaham guitars do a MIM upgrade pack which is designed specifically for upgrading mexican fenders, so that would take care of the bridge parts, you'd maybe get a bit more sustain, and perhaps a more detailed tone.
Electrics should be fine, you could replace them too, but I wouldn't bother unless they were broken. If you like the feel of the neck, it's a nice neck, and replacing the neck or the body is more like building a franken-strat than upgrading it really.
If you made all these changes, there's no real reason your mexi shouldn't sound every bit as good as an american. Take it for a pro-setup at a decent music shop too, have them check the fretwork and everything. Voila... Gorgeous sounding strat
