A big reason why people abuse the ER when they don't have an emergency is that they do not have insurance or an ability to pay out of pocket. So, like Daihashi said, they cannot be turned away or forced to pay at the ER, and they end up going there for minor injuries or illnesses that are not emergencies because they won't be seen at all anywhere else.

Unless the clinic-in-every-Walmart plan solves the problem of being able to PAY for the care, it won't solve the ER abuse problem. Universal healthcare coverage will solve that problem by removing the economic need to use the ER for non-emergencies.

ER abuse is just another way in which we all pay for a healthcare system that leaves out millions of people. Even if it cost us all more in taxes to have universal coverage, we would all see some benefit in not having our ERs clogged with non-emergency cases who are only there because they cannot pay, and we would all see some benefit in not having those people's ER costs added to our bills to cover their non-payment. Getting everyone who is currenlty uninsured into a system where they can get preventative care, and the costs of their non-payment do not get distributed to everyone else, and there are not unnecessary ER visits is going to save a lot of money an inefficiency in the long run.