candycane is correct.
Nothing at all would happen, if you want to practice in the US... the US internship takes place after graduation as the first year of specialty training.
Also, since Poland is an EU member, you would likely be fine for training/practice the EU, as well. In the event that a country wanted you to get more hands-on experience, then you could certainly get it. It's not a huge deal for those locations, anyway.
"To array a man's will against his sickness is the supreme art of medicine."
- Henry Ward Beecher