Not American but have lived there for almost 15 years now...
First, it's scattershot. The whole premise is that the whole thing is done in under a week. Sometimes the writers are brilliant and sometimes they scrape the bottom of the barrel. It also depends on the host: Some are good live, some are game for anything, some are awful. You can really tell when they're bad because they'll try to keep them out of the live sketches. My kids watch so I do.
Some of the humour is definitely American specific, like the ones dealing with specifically American culture. Great example: The John Mulaney and Ego Nwodim sketch where he goes to a Black wedding, and you think the whole setup is that he's nervous just because he's white, but it turns out he's very familiar with Black culture. All the references are great, but I don't think it's funny if you don't know them. Or the skit where Marcello Hernández brings home his white girlfriend and Pedro Pascal plays his mom and 3/4 of the skit is in Spanish. And of course some things are parodying American shows or ads.
(The lingerie store skit with Anya Taylor-Joy is one of my favourites, but it's also very clearly a parody of certain NYC bra stores. Anya really nails the accent, too.)
SNL also has a tendency to run characters into the ground if they're successful and it usually brings diminishing returns. Last night's anniversary special had a lot of those. I'm not sure Dooneese needed that many airings, no matter how funny Kristen Wiig is (and again, most British people don't know anything about Lawrence Welk).
They also repeat setups too much, like game show skits. The political comedy is incredibly up and down. It depends partly on the writing, partly on how the impressionist sets up their version of the character. Melissa McCarthy's Sean Spicer was brilliant because she latched onto his bombast and turned it up to 11. One of the Biden impressionists was terrible because his take was simply "He's old and gaffe-prone."
At the moment I would say the cast is middling and the writers need a refresh, but honestly the fun of SNL is the not knowing what's going to happen. It might be funny, it might be terrible, and you've got to stay up till the end if you want to see the writers pull out their weirdest ideas.