Wow - that is a question that would require a book's worth of info to properly reply to. I used to work for a Fender dealer and STILL have trouble keeping it all straight...
The important parts are these: The mexican made strats are really very good. The bodies and necks are made to the same specs as the USA parts then are finished in Mexico. The electronics are not as nice and the pickups have ceramic magnets rather than alnico, resulting in a hotter but less "vintage" sound. Bridge is a different metal compound which some argue is not as resonant... Overall good guitars though, and the Mexican Classic Series Reissues are VERY good.
The USA models are very nice. More consistent from one to another and more modern in construction. Better pickups,
bridge saddles, tuners, fretwork, etc. Find a good one and it will last a lifetime and will sound GREAT. They come with hardcases rather than gig bags and will take a beating.
Then there's Highway One Strats, Deluxe Strats, American Vintage Strats, Special Edition Strats........ ugh..........