Whether an ER looses or makes money depends on the number of patients without insurance and government reimbursement for indigent care. This varies a lot from community to community and state to state. For states with expanded Medicaid, ER loses should be low in most communities.
A lot of hospitals in California went bankrupt because of so many illegal aliens who didn't pay. Illegal aliens run up bills having lots and lots of anchor babies. Hospitals in areas with high percentages of illegal aliens are most likely to go under.
Obama claimed that Obamacare wouldn't cover illegal aliens, then he made sure they all knew that no one would ask about citizenship when they applied for it. For some reason, a lot of people still aren't signing up.