It’s hard to flunk of a US med school. The 6 year graduation rate is 96.1% ( SIx years to allow for multiple degree programs like MD/MS, MD/MBA. MD/MPH and MD/PhD)
The #1 cause of med students failing to graduate is dropping out due to mental health issues. Med school is a pressure cooker and suicide is the leading cause of death for med students. (Cancer is #2.) Med students are three to four time more likely to report having depression and suicidal ideation than their age peers.