Agree with previous poster. A US high school diploma in itself will generally NOT be deemed equivalent to most European baccalaureate exams (A-levels in UK, Abitur in Germany etc), and while it's sometimes possible to gain admittance, European med schools are generally very competitive, just like in the US, so you'd have to be a pretty strong candidate. Also, remember that the entire medical system is quite different in Europe compared to the US, and thus a European medical degree wouldn't train you particularily well for working in the US.
If you want to practise as a physician in the US, I'd strongly encourage you to get a US undergrad. degree and apply to a US medical school.