Possibly it was just a case of wishful thinking.
If GM, or any domestic manufacturer, had the ability or DESIRE to build a vehicle as well as Toyota they would not be in the poor situation they are in now.
I am reminded of the group that GM sent to Japan to find out how they built such good cars. They sent engineers, designers, accountants, and even union representatives and assembly line workers. The DESIRE was there. They wanted to compete. However when the group came back they told executives that the secret to building a quality Toyota was no secret at all. It was the people. The people took pride in what they did.
Nevertheless GM went ahead and built the Saturn plant as an answer. They still have not and will never pay off the $3billion burden to build that plant.
That being said if you compared the quality of US cars to Japanese cars in say 1990 a Toyota may have scored a ten and a ford a 5. Today it is more like ten to nine. We do make quality autos in the United States but they make them just a bit better in Japanese factories. Nevertheless the Japanese admit they cant get the quality in their US factories that they get from their Japanese factories. Even Consumers Reports say that if they used the quality criteria today that they used in 1970 every car would get a black dot... or is it white?
Most of this paraphrased from a Car and Driver article a few years ago.