Adding USA zone to www.usasellbuy.com

I have a classified ads website.Web site : www.usasellbuy.com .Web site will work only in USA.

While any people posting ads : he / she must see -States, cities, town,district in USA – in ads section.All zone informations ( States, cities, town,district ) automatically must be seen in ads.So he can easily select address of any property or any goods he wants to sell.