Consequences -International Collection Agency- Mexico

Im from Mexico and last year I had to go to the hospital in the US for a sharp abdominal pain. After 3 ER visits and 1 day admittance and a terrible treatment (that included them not giving me the correct diet to follow which made me go to the ER for a 4th time, DR not available for follow ups and even suggestions of me trying to get easy drugs from them), I was charged with $42,000!

My insurance in Mexico first wanted me to cover the whole bill and then reimburse me with 80% of it. I know learned that they have already covered 80%.The hospital wants me to pay 20% or ($8,400). They have already hired an international debt collection agency that has been sending me letters.

What is the worst they can do?
Can they affect my credit report here in Mexico or anywhere else I live at?
I have no property yet but can they go after my parents property if I said I depended on them economically?
Can they make my insurance company in Mex to force me to pay?
Will I be stopped at Immigration if I go to the US as a tourist? Can they make the gov revoke my tourist visa?

Thanks for your time!