What is the softest riding American made car?

What is the softest riding American made car?
There is no good answer to this question as the 'softest' ride is a function of the road, driver's skill, shock absorbers, springs, and seat support, as well as the age of the equipment involved. Plus, what is 'soft' to one may be mushy to another.
If you want a 'soft' suspension, don't get a sports car. The suspension is 'tighter' in these cars so they don't 'lean' as much in high speed turns. Also, vehicles which are higher off the ground are often 'softer' rides because to elevate the vehicle, one of the tricks they use is larger springs. Larger springs give you more a cushion and the better shock absorbers keep these larger springs from from bouncing repeatedly when you hit a bump or whole. Of course, none of this matters if you are driving down a gravel, pot-holed road. You will get a bumpy ride. But on a smooth road, even a sports car has a soft ride in a straight line.

My advice is to get a SUV if you want a 'softer' ride. Or just sit on a pillow....