EMS and ED services, along with an explosion of medical debt. They're already loaded to maximum and often times in straight up overflow - several of the counties near me have wait times for EMS, and the ED'S always have lines in triage and people on halfway beds. The system is running at or slightly over capacity most days, and it just breaks in the period between Christmas and New Year's. And this is a system in a Capitol city that's fairly populous. Rural hospitals are barely holding on between staffing issues and funding shortfalls. COVID decimated the number of nurses working in the US and the numbers still haven't recovered. Times were you didn't make it into a NICU/ICU or ER without several years experience and a good resume, now they take anybody breathing.

That's bad, but if those Medicaid cuts from the budget bill go into effect it'll implode. A large portion of EMS ground ambulance costs are paid by Medicaid; if people are forced off the program or the reimbursement drops too far, it straight up won't be affordable to take Medicaid patients. If that goes, a number of ground ambulance operations will have no choice but to close their doors, which will leave city fire departments on their own to figure out funding and non-emergency transports like return to homes or hospital-to-hospital transfers.

This will, inevitably, lead to reduced compensation but paradoxically a bigger number of people going to a hospital ED (if people can't get routine Healthcare, they wait until it's an emergency. This happens already and is a large part of why the system is at or overloaded it's capacity). They'll just drive or walk or bus or otherwise transport themselves rather than use EMS. So you'll end up with people who can't pay, showing up to an ED with preventable problems, waiting a really long time to be seen. Wait times are already an hour or more, prepare for them to get ludicrously long. The reduced or missing compensation to the hospital for services rendered then has a whole bunch of knock on effects - people in medical debt from using ED services, but also prices going up elsewhere because of the reduced ED income. This makes health insurance more expensive, denials more common, reduces quality of care, etc. And this is all just looking at hospitals in urban centers. Rural hospitals are just fucked.

Tl;dr, if the Medicaid cuts go into effect, non-zero chance significant portions of the US Healthcare system become unaffordable or collapse entirely.