At BNA, there should be some empty capacity for the US flights in the AA gate area.
US uses B6, B8, and B10 but only for 15 flights a day, but both US and AA fly BNA-DCA so I'd expect a few of those frequencies to go away.
AA uses the C concourse, gates 3, 5, 6, 10, 12, and 14 for about 35 flights. I believe that C2, C8 and C11 are currently not used but in the AA gate area.