Become very green and very cheap.
Also have better marketing and become unique in its designs.
Other answers are more complex, like change the roads in the US so that they are interesting and so that there is a point to make cars that actually handle or change the state of minds so that people change lanes and start driving like Italians (what's called rackless driving in the US of A) or in other words take a chance instead of being rich petit borgouas.
The problem is a deep social one. Empires fall because they lack something to want and because their system of values has too many internal contredictions. The US believes in taking chances and being pioneers but has too much to lose so the people act cowerdly, hence their cars are not interesting. They make cars for people that want to move predictively and this is far from thrilling. They make SUVs for people who do not go out of the paved road (because they fear the wilderness as much as they adore it) and this is really patetic.
But all this is hard to change, so I would stick to money because that's what they know best - green and cheap.