It is indeed: American audiences love characters that are basically just conduits for "does the ends justify the means"-type plots.

I think The Wire is a bit better than that, though: the moral ambiguity in The Wire seldom boils down to justifying the means: plenty of characters are just bad in an individual capacity while doing good in their professional capacity, or vice versa.

The Omar character is probably the most straightforward in terms of the trope, but even he does not act for the sake of the ends: he does it because it's all he knows.

Sure, it is now, but was that the case 20+ years ago when The Wire first aired?

I think it's become more common, but the subgenre of "surveillance" media has always had elements of this. Compare The Conversation (1974)[1], for example.

[1]: https://en.wikipedia.org/wiki/The_Conversation

Han shot first. Also, like every movie starring Clint Eastwood?