I'm re-watching The Wire. He's supposed to be a cop from Baltimore; I suspect his accent wouldn't be recognisable as a Baltimore accent to anyone familiar with it. I think he actually struggles to sound authentic as any kind of US accent.
Almost no one in the cast, including the Americans, save for the 3 actors from the area (Robert Chew as Prop Joe, Felicia Pearson as Snoop, Anwan Glover as Slim Charles) even tried putting on a Baltimore accent. Wood Harris and Idris Elba were supposed to be dealers from the Baltimore projects, but Harris just spoke in his Chicago AAVE accent and Elba sounded like a guy from New York City (his accent even breaks pronouncing the word 'responsibilities'). Lance Reddick sounded like Lance Reddick. Robert Chew tried coaching the kids in season 4 in a Baltimore accent and dialect but the accent didn't seem to land.
I do wish David Simon had enforced accents as strongly as he did with Treme.
I can't understand Snoop at all. I've watched this stuff more than once. I still can't make sense of what she says. I know the actress is the real thing.
I thought she was a bloke with a high-pitched voice the first couple of times I watched it. I guess her making like a bloke is part of the character's backstory.
I think he's great in the part, though.