First of all, if people buy American cars out of patriotism, American car companies have no incentive to improve their product. So you're not really doing them a favor.
Secondly, there really is no such thing as an 'American' car anymore. Every car made in the US is made by a joint venture between a US company and a Japanese company. Ford and Mazda, GM and Toyota, Chrysler and . . . well it used to be Mitsubishi but now it's FIAT! We developed the science of reliability and quality control, and we taught it to the Japanese after WWII. The WE didn't do it, THEY did, and they ate our lunch. Then we had to have them come here and show us what we showed them. US cars have gotten better in the last couple of decades, but they wouldn't have if not for the competition from Honda and Toyota.
Back in the 1980s, Ford spent hundreds of millions of dollars on a study to see why it was that Americans preferred Japanese cars. I could have told them much less. They learned It was because Japanese cars lasted longer and had less trouble. Then Ford decided to spend a BILLION dollars, over a few years, not so much to improve their quality as to improve the customer's perception of their quality. Their motto was 'At Ford, Quality is Job One'. If you're old enough to remember this campaign, their spokesman was Bill Cosby!
The fact is, many Toyotas ARE made in the US. Some are made in the same factories that make Chevys. And many 'American' cars are made in Mexico. (Nothing against Mexico, but it's kind of dishonest to call them 'American' cars.)