A few days after sighting these birds in my backyard, I spent a little time on Cornell’s All About Birds.org as well as on Whatbird.com, which has an excellent visual step-by-step search function that allows users to choose particular visual characteristics to whittle the selection down. It’s an excellent tool for beginners like myself.
My current theory is that this is a female (or possibly juvenile) mountain bluebird. This is the closest match I can find. The odd thing is that mountain bluebirds aren’t generally found in North Carolina; this would be way out of its range. Perhaps it shouldn’t have taken that left turn at Albuquerque.
Here’s the ID from All About Birds.
I’ll ask around and see what more authoritative types might have to say.
MissingHenryMitchell 
We have a pair of Mountain bluebirds that nest next door every year, and I think yours is more likely a juvenile Eastern bluebird, which are similarly spotted to the juvenile Mountain bluebird (making it easy to mix them up). The Eastern looks to be a little longer and sleeker than their stocky cold-climate cousins. If you do an image search for “juvenile Eastern bluebird,” there are several pictures that look like a match for this young adventurer.
Thank you so much!