By multiple measures, U.S. access to medical care lags behind that in other developed countries. Pediatrician and medical school professor Aaron Carroll talks about that here:
For more on this, see Dr Carroll's article in The New York Times from last October.
Yes, I'm a little late posting this, and for that matter Carroll is talking about research conducted several years ago, but it's still relevant today. In fact, just a few weeks ago I gave up getting an appointment to see my primary care doctor and wound up going to an urgent care clinic.
There seem to be more and more of these, some of which even specialize (for example, in orthopedics and sports injuries). Even drugstores and discount retailers have clinics, often staffed by nurse practitioners or physician assistants. Carroll has mentioned these in the past, and do they help make up for the shortage of primary care doctors as well as providing an alternative to going to the emergency room with something that isn't a real emergency.
A walk-in clinic isn't a perfect substitute for a primary care doctor you can see on short notice. There's a lot to be said for seeing a doctor who knows you and has access to your medical records, and who can update those records to reflect your latest illness. A bit of good news is that more and more often doctors are affiliated with medical centers and accountable care organizations that have a shared medical records system and very likely one or more urgent care clinics. Unfortunately there's no guarantee that all your doctors will talk to each other. The large orthopedics practice I visited a few weeks ago seems to have an excellent medical records system, but it doesn't talk to the one used by my primary care doctor's practice, which is part of Duke University's healthcare system. Neither of them talks to my dermatologist or my optometrist or my dentist as far as I know.
France seems to have solved this problem, but we're still working on it.