I'm pretty familiar with most of the trees in NC, and I can't hang a name on that one from the pics. It's not sassafras. If I could see it in person or get a better close-up photo of the twigs and leaves, I might be able to tell you. The bark looks closest to black willow, mulberry, or eastern cottonwood, but the leaves from what I can see in the photo look like none of the above. It could also be a non-native escape.