>I'm in the US and have no insurance. How much should I expect to pay?
Nothing, of it's a hospital visit. Ignore the debt for a few years and it will go away. DO NOT RESPOND to any mail. The debt will eventually default and the company will be compensated by government bailouts. Just don't expect to get treated well if you go back to the hospital.
Same with doctors, but they're usually more reasonably priced. Probably a couple hundred, less than a hundred for a checkup. If you do any procedures, it'll jack up the price. Drugs will cost a few dozen to pick up at a pharmacy. A checkup will be a couple dozen on its own.