If I was you, I would rent a car and go around the town, get a good meal, do the Charlotte must do's (I duno what are things to do, but there must be some good places to go to).

When I have time to kill at an airport, I sometimes just go get some local gifts for my wife/daughter.

With $149, you should be able to do a lot of stuff better than going to a US lounge with NO showers.