Wrong country (Mexico instead of USA) at set-up of App

As I live in the US and work in Mexico when I set-up my account when passing the border it took the Mexican GMCapp and now it always connect to the http://www.gmc.com.mx site, which wouldn't be a problem to me, but it doesn't allow me to put in m US address as it gives only Mexican states instead of US states. So how can I change this account to a US one.

If not passible, I probably discontinue the service after the trial period. My VIN is : 3GTPHCED8TG294543