After reading this thread yesterday, I Googled 'American oil imports' and discovered that 58% of your petroleum was imported in 2007. If Americans are so concerned about local content in their cars, would they refuse to fill their tanks with petrol (gas) imported from Mexico, Canada, Venezuela and the Middle East? You might be spending more on imported gas than you are on imported parts each year!
Speaking as a 'foreigner', we are all proud of cars produced by our own countries - I used to buy 'British' cars even though they were not 100% British. I'm sure something similar applies to our other 'foreign' members too from France, Germany et al.
My passion was (and still is) Fords, and although I knew they were ultimately American, cars such as Anglias, Escorts and Cortinas were not marketed/built over there, so I regarded them as 'English' Fords. Later they became increasingly 'European' but I still purchased them.
Very few manufactured items are 100% local, get used to it!