I mean it’s pretty clear why it’s stubbornly Republican: it’s suburbs haven’t gone the way of GA, ILL, CA, NJ et cetera, et cetera..
But Biden did actually improve in NC suburbs (Wake and Mecklenberg) compared to Obama's 2008 margin. It really is just the case that North Carolina is still a much more rural state than GA or VA and, as a result, Democrats have actually bled a lot of votes there over the past decade. I also don't believe North Carolina has been getting appreciably less White in the same way Georgia has.
