Addressing capacity? In a country this allergic to infrastructure investment?
It is difficult to find a commercial airport, of any size, in the US that doesn't have current infrastructure expansion projects underway.
EWR just opened the new Terminal A and work is proceeding to remove the old terminal which will allow all of the new gates to open.
LGA has significantly upgraded and improved the main terminal and continues work upgrading and expanding.
ORD has completed a multi-year project building additional runways, now allowing configurations with three simultaneous arrival runways and two simultaneous departure runways. The expansion of Terminal 5 is complete while remodeling continues. Taxiways are currently being relocated to make room for the expansion of the C concourse and addition of another concourse west of that. These concourses will allow the replacement of Terminal 2 with a new international arrivals and CBP facilities and more gates.
BNA is in the middle of a multi-year expansion and improvement project which will include a new CBP facility, a new D concourse (completed), on-airport hotel, remodeled C/B concourses, expanded and remodeled A concourse, and a satellite concourse. Road construction is underway to move the bridge over I-40 to the east to increase the space available for the airport for parking and traffic management.
SAT has a new terminal.
MSY has a new terminal.
MCI just opened a new terminal.
SFO recently opened new concourses and air-side connections between them.
IAH built the new north C gates and is currently in the process of rebuilding and expanding the D concourse and the E/D Terminal.
SLC has a new terminal/concourses.
DEN has extending each of their three concourses, both on the east and west side of each, and the main hall reconstruction is continuing.
LAX has a big update and expansion ongoing on the north side and the elevated people mover project ongoing which will relieve the traffic congestion in the big "U". The TBIT west terminal has been expanded with additional concourses. Construction of Terminal 9 is planned.
IAD is working to replace the old A Concourse with a new concourse over the "C" train station, just opened the airport link to Washington's metro, and has just started the process for replacing the "temporary" C/D concourse build in 1985.
SAN has a large construction project going now which will increase parking and upgrade/expand gates.
DFW is going to build a sixth terminal.
MCO just opened a new terminal and intermodal transportation facility with links to Brightline's rail service.
So, lots of infrastructure improvements recently completed, in progress, and being planned.