That's not all of the reason (some of it is higher cost of living, compare G20 vs G7 and the gap narrows a bunch). Some of the reason is because of US education costs, and immigration policies that make it harder for people to come and work in healthcare.
Does it? Average physician cash comp in Germany is 75kEU, and average cash comp in the US is something like $350kUSD. Note here I'm using one of the largest and soundest economies as a comparison, and one with substantial uptake of private health insurance.