In my opinion, this won't stop you from from enjoying Infinite Jest. There are a few arcs that might require some insight into American culture (Professional Football, the US drug rehabilitation system). But the big picture themes are either very universal or so particular you aren't really expected to be keyed into them (you don't need to be a competitive tennis player or a Quebecois separatist to enjoy it).

Pale King might be a bit of a different beast. The focus on the IRS is somewhat particular, and you may miss big beats because of ignorance about the IRS. But at the same time, some of the accounting minutiae are such that I don't think you're expected to understand them.

Anyway! I wouldn't let this steer you away. To me, the joy of DFWs writing is the individual sentences. The mannerisms and humanity of the characters. If you miss some details because they're US focused, I don't think it'll be anything important.

For what it's worth, I'm British and even though I didn't get all the cultural references in his essays, it was usually easy enough and read between the lines to infer what he was hoping to illustrate from his examples.

This happens a lot in one of my favourite DFW essays, E Pluribus Unum, which although a little dated, still does a great job of illustrating the impacts of "self-aware" media consumption, and how it affects the richness (or lack thereof) of culture.