Campsis radicans has much more regular, pinnate leaves. Ampelopsis arborea occurs in Oklahoma. Here is a link that might be useful: Ampelopsis arborea

Looks like a Sedum, maybe S. rupestre. If so, a full sun plant, creeping ground cover that shouldn't need any watering except in case of serious drought, hardy to Z4. http://davesgarden.com/guides/pf/go/3294/

we are in eastern Mass, but not sure if considered "sandy" part! If you mean along the shore or down near the Cape, then no. About 25 miles southwest of Boston. It does seem bent-like, and I've almost always had tufts and patches of bentgrass (the bane of my existence in what is otherwise kbg, rye, fescue mix) and this seems way more aggressively vine-like. While the other bent patches are carpet-like, this one is more like a clump with 1 definitive vine. The clump in the picture is just one that is lonely in the mulch bed, but the lawn itself near this area is a whole big patch of this stuff. Thank you!

I think Skelly is right! I say that as I grew morning glories in my vegetable garden about 7 years ago and I still am battling little morning glories coming up. The small plants I pull out resemble yours very much. I think you have the wild morning glory.