If the packaging is marked MADE IN ..... that's your first clue as to point of origin. Also, if it is an aftermarket part, look for the appropriate Big 3 logo and a statement indicating that this is a factory approved aftermarket part. GM, Ford and Chrysler have been granting licenses to aftermarket companies around the world for years. To get the endorsement, you have to submit prints, samples, etc just like a Big 3 supplier has to do if they are supplying a new production part. It's the no-brand stuff that shows up cheap at swap meets & flea markets that you really have to watch for. Also, if in doubt about an item, contact the appropriate car company's customer service department. They have lists of who is approved and who is not so they can advise.
Also, remember that it is common for vehicle makers to make running changes in their products and that sometimes you need the "old" or the "new" version of an item as they may not interchange (you have to drill holes, bang them into place, etc).
