Bottom line is if you purchase an American made vehicle, even if it was made in Mexico or Canada, you support more US based jobs. I've heard ratios of anywhere from 6:1 to 15:1. That is if you buy a Chevy, Buick you've essentially helped employ 6 US citizens, whereas if you buy a Toyota, Honda, etc, you would only benefit 1 US employee. Assembly is just 1 small portion of the entire manufacturing process. Just cause it's put together here does not make it an American vehicle.
I've always been and always will be pro USA. But, hey it's a free country, thanks primarily to our military past and present, so we can say and buy whatever the hell we want!