Why might the humor in Seinfeld not translate as well to British audiences?

What the title says. I’ve been told by multiple Britons that they “don’t get” my favorite show or understand why Americans find it so funny. Granted, they don’t speak for all their countrymen but the pattern is noteworthy.

Is Seinfeld so uniquely America-in-the-90’s that it simply doesn’t translate to other places?

For what it’s worth, my follow up is usually whether they find Always Sunny to be funny, and the answer is usually yes.

Thoughts?