Medicare for all doesn’t get you “training cases”. You are misunderstanding residency training.
Say you work at a widget factory. To be proficient at making widgets, you need to produce 1000 over the course of 4 years. The factory has enough supplies to hire 100 widget makers. The public screams, we need more widgets! Make the factory double their widget makers. So the powers that be pass a law. There are now 200 widget makers but still the same supplies. So now you have one of 2 outcomes. It takes twice as long to get proficient at making widgets or you are training subpar widget makers that make subpar widgets.
They have their own unique history of racism, ignorance, and innumeracy. None of those faults are singular to the USA.