My favorite American ones are
Batman: the animated series
South park
Rocco's modern life
Sponge bob
King if the hill
Boondocks
My problem with American shows is they ever end. Uk doesn't have this issue.
Japanese ones
Haibane renmei
Ghost in the shell
Planetes
Steins gate
NanA
There's a lot of other good ones, I find it irritating that this turns into a dick measuring contest when both have a lot of acclaim. I don't see it as us vs Japan... Because those are all pretty much better than all shows everywhere imo. Japanese plot is a bit more varied. American animation is a bit more varied. Batman for instance was made by Japanese and korean animators animators as was ninja turtles. Disney had a ton of Japanese animators in their heyday.
I like fringe, star trek, breaking bad, red dwarf as much as those shows too. Idc good shit is good