From the late 50's to the early 70's the best handling luxury sedans made in the USA were the imperial crown lebaron sedans for these reasons:
-the torsion quiet ride featuring semi elliptic heavy duty leaf springs in the rear with rear torsion bar with specific insulation and front independent suspension with front torsion bar
-fast power steering ratio
-413ci then 440ci v8 engines which are bulletproof engines and long lasting
-also the biggest passenger space and trunk volume back in the days for the 1969-1973 models.
But this was the past. And in the past Imperials outhandled Lincolns and Cadillacs even some high end european cars such as Jaguars or Mercedes. For instance the Chrysler 300 letter car series were the best handling cars of the late 50's early 60's, even back then few european cars could touch them nor even compete with them.
But for the modern car era, is the cadillac seville sts a bad ride? I don't think it was, and it was one of the best american made cars alongwith the eldorado tc, both with front wheel drive and the northstar 4.9 v8.
For sports cars, there was the zr1 and later the z06 which were and are offering a serious run for the money against their european counterparts.
In the late 60's /70s, Mustang had the 302 Boss and Chevy the Camaro Z/28 were both used in transam racing with success and the civil versions of these cars sold quite well. Pontiac came with something special in 1973, the transam with the 455SD (super duty) perhaps one of the best engines ever made in the USA and which made of the transam one of the fastest production cars and one of the best handling one too.
I think that bad tires especially the polyglass and the wide oval tires were penalizing the handling of American cars back then. Also the suspension on some luxury cars especially Lincoln and Cadillac in the past (especially 50's to 70's models) was too soft unlike on Imperial cars. With modern tires and stiffer shocks these old cars have a lot of capabilities.
I probably will never be able to convince you that American cars handle quite well and for a number of them equal their European counterparts but offer more fun. There are some cases where I will rather have a German car instead of an American one or an English made one.
Have a good evening and a nice sunday
Regards
Georges