I know a Canadian who had a retina detach while in the States.

She went to a Dr. in the states. They determined she needed surgery immediately.

Unfortunately, the local hospital would not let her have the surgery. Why? The billing department was closed for the weekend. She offered to pay cash. Still, the answer was no. The surgery was delayed for 3 days. In that time, she her situation severely worsened, causing permanent damage that would have been prevented by surgery.

She immediately made an emergency trip the Vancouver -- and was treated the same day, surgery and everything. No cost.