Sort of. The US medical system has multiple choke points, but an undergraduate degree is the least limiting. The bigger barriers are the limited number of med school spots and the even smaller number of residency spots. Med school is a whole discussion, I don't even think you should need an undergraduate degree, but whatever. The final filter is residency spots, which are functionally set by the government. They pay hospitals to take residents, and will only pay for a certain number each year. We gotta increase that number if we want to stop throwing away educated doctors before they can even get to helping people.