@amarand They both "generally suck". Your perception is skewed by selectivity of the British TV that gets exposure.
Spend time in U.K. watching everything broadcast. Lotta crap there, too. Reality shows, game shows, low grade documentary shows (all cheaper than scripted shows.)
On balance, if constrained to broadcast, more variety in U.S. Most is crap, but more volume means more good as well on any given night.
Arguably the "best" British shows may be better than the "best" U.S. though
@amarand I find shows I like on Netflix and Prime and Apple are dominated by British actors. Not sure if those are "British" shows. Wheel of Time, Outlaws, Slow Horses for example.