Yes.
You can order a significant variety of antibiotics over the counter / web in the US. I have 2 Z-Paks, a bottle of Amoxicillin and a bottle of Doxycycline sitting in my medical drawer. You can order them legally via US based online pharmacies. If you are an adult you should have the freedom to treat yourself. Freedom does not absolve you of responsibility though. If I mess myself up I have no one to blame but myself.