I would agree with Med_Heidelberg, German medical students tend to score very well on the USMLE, so that should not be much of a problem. I know a bunch of foreign students here in Freiburg who came to Germany without being fluent in German. After taking their Sprachkurse they did quite well on their language exams and are studying very successfully now...so the language barrier shouldn't be too much of a hurdle for you.
If you consider studying Medicine in continental Europe, I would recommend Germany, the Netherlands, or maybe France. Coming from the US, I can speak highly of the medical education here in Germany. From a fellow student who transferred to the Netherlands I have heard, that medical schools there are very good as well, and the same goes for France. The east German medical schools (e.g. Dresden, Leipsic, Jena) often have very nice facilities, as many were modernized after reunification, though the big names are naturally a safe bet for an excellent education (Heidelberg, Freiburg, Tuebingen, Munich, Berlin). Good luck in any case!!