Danville is on the VA/NC border. I'm sure there were plenty of North Carolinians in the audience, and it's been a well-known strategy that excess resources and virtually all volunteers from adjacent states (TN, GA, SC, VA) be directed to help out with the NC campaign via phone banking, canvassing, etc.
Considering that Virginia is a swing state that Obama really needs to win the election, I doubt there will be many Virginians wasting their time trying to win a state that leans even more Republican. They will focus on Virginia.
It's pretty clear that Biden was supposed to say Virginia.
