I think American automakers have made all the initial advances into automotive technology from the very beginning.
Using an assembly line, robots, on-board computers, ABS, and hydrogen fuel cell technology were all American ideas. They started first, had the lions share of the world market, and many other advantages at the outset, so how did it come to this?
A lot of it wasn't the automakers fault. When steelworker unions forced the government to impose tariffs on imported steel to support local industry, it hurt Detroit. When foreign nations limited imports of American cars, and trucks, it hurt them, and Detroit. When America became increasingly hostile to business, it hurt Detroit.
What things they did to themselves to create this position was capitulate to the unions. That began the end. Another problem was increasing their coziness with lawmakers for special privileges. The government was already acting like a social battering ram, so hey, why not get on the good side of it?
Their management also made some serious blunders. They concentrated on short-term sales instead of long-term growth. They didn't see an end to cheap oil, and were unprepared for the oil crises of the 70's. They didn't invest in the robotic technology that the Japanese were beginning to use because the UAW wouldn't let them, but it was already too difficult to move plants overseas by that time. They also concentrated too much on sales and not enough on quality. They had plenty on their staff for marketing, but not enough for engineering. What engineering they did involved planned obsolescence, and that eventually came to bite back at them as perceptions of lack of quality came from that.
The stock sales to the Royal Saudi family also hurt them. Having that many shares insured their people on the board, and those guys didn't want to move away from gasoline, or big cars.
So it was a combination of screwing themselves, getting screwed by foreigners, and getting big-time screwed by the government that led to this.