I think the reason we know British comedians better is because they have more of an opportunity to feature prominently on TV due to things like Taskmaster or panel shows (aka actual good shows where they can talk a lot and have a lot of opportunities to be spontaneously funny).

In the US there's @midnight, but it's bad, hurried and hard to really get to know each comedian, and other shows tend to not be great either (I can barely even think of other shows where comedians go as guests, but I know there are some out there). There's also an opportunity for stand ups to perform on late night talk shows, but nowadays it's rare to see any comedian more than once cause there's too many of them, so you end up not really remembering anybody's act.

So basically, I think, it's hard to be a "medium size" comedian in the US. You're either small time or huge. In the UK it seems there's the small guys few people know about, then the "medium size" guys that do the occasional panel shows, followed by the "big" guys that are well known but still appear rarely on panel shows (or are "team captains" on some show) and finally the huge worldwide comedians like Ricky Gervais.

I know some of this cast (Lisa was on some Comedy Central Roasts, like the Roast of Donald Trump and she wasn't great. Ron performed on a couple of late night talk shows, but I don't remember if he's good or bad), but I'm someone that knows more than the average person about comedians in general because I watch a lot of stand up and do things like listening to comedians' podcasts (in which they frequently mention smaller comedians friends to help them out).