yup he will pick up the slang and a bit of an accent after a couple years, but he will always be a dang yankee...
oh lord a yorker with a southern accent yup best he says nothing that would like trying to talk with somebody from boston.. nobody would be able to understand them.
after 17 years out here i still get your not from here are you...nope born and raised at lake tahoe california, oh thats in southern california ..

one too many paint chips as a child. heck there are some towns that still get their sunlight shipped in....
while on my extended stay in warsaw,nc meet the g/m for the first time, oh my he was from portland, marine. oh did i have fun with him....dang maple head go home......
as for an texas accent, it depends on how much gun oil they were given as a child when they had a cough.....
all kidding aside being from california, neutral to all the funny accents yankee/southern will just leave it that .....