I know someone who didn't match, but it was mostly likely due to poor application strategy. Any US MD applicant without red flags should easily match somewhere decent. There are a small number of people with 8+ interviews each year who don't match, but I imagine most of them have severe interview problems or have something come up (like a Step 2 failure) between ERAS submission and ranking time.
Usually US MDs are still able to get a spot. But, it is harder. Programs are looking at Step scores in Psychiatry now. Things are definitely getting more competitive.