As a non-native speaker, it's definitely impossible for me to understand every detail of the conversations in The Wire. Especially the jokes.

But it's an interesting show anyway, even without the details.

I grew up in urban DC + public schools and I found it relatively understandable without subtitles, although perhaps not every single thing (some specific slang terms).

> not always in easy-to-understand dialects or accents

I'd never really considered this. Grew up in the south-eastern US, with one side of the family from the Northern Neck of Virginia.

Accent was definitely Baltimore, but I never had an issue.

The Chesapeake Bay definitely has a lot of interesting accents on various sides, though: http://aschmann.net/AmEng/#SmallMapCanada

Mos' def' bro.

And I mean, they do have a scene where the cops have to hire a local lady who speaks the slang well to transcribe some of the conversations.

True that.

I watched The Wire with my Italian (from Italy, not Italian-American) in-laws. Even with subtitles, I'm pretty sure they missed a lot of the story.