I am American and I'd have a hard time picking out their accents. FWIW, I'm from the upper Midwest where we all sound more like Vince Vaughn. I agree that Owen sound a bit more Texan, but I'd probably have guessed California if someone asked me to say where they're from just based on their accents.
If they sounded exactly like they do, but were from Europe everyone would say that their accents are terrible and that no one here sounds like that.

He was born and raised in Dallas, Texas, and spent a lot of time in Austin Texas, but his Wiki entry says his family were originally from Massachusetts.
The thing about many metropolitan, educated Texas people, though, is that they don't really have the stereotypical Texas accent and often do sound like just "neutral" American maybe with a tiny twang. Oddly his brother Owen sounds more Texan than Luke does.

It's not exactly a Texan accent, it's the way he speaks. actually both brothers Luke and Owen speak in that style, must have got it from their parents.

he's from Texas