Closest one that I am aware of in Texas at least is the East Texas Model Railroad Club (ETMRC) .
It's located in Commerce, about 120 miles from Texarkana. It is the only one that I am familiar with. There's two in Shreveport LA, which is around 75 miles from Texarkana, the Sue Line Railroad, and the ARK-LA-TEX HO Train Club. Don't know about Arkansas.