The best, or perhaps the most significant US made convertible ever was the 1957 Ford Fairlane Skyliner.
It was the first US car with a hard-top that folded into the trunk.
So, with the top up...no wind noise. Also, enhanced vehicle security, and perhaps roll-over protection with the top up.
AS for the best looking US made drop-top... It's a toss up between the '57 Corvette, the '56 T-Bird, and the '65 Mustang.
Honorable mention to the 1967 Chevelle/GTO, The 1961-63 T-bird Sports roadster, and the 1955 Chevy.