We had occasion to experience an ambulance trip from Lake Louise to Banff, then an overnight stay in the ER at the Banff hospital. We did not have travel insurance, and our US health insurance was not accepted. Our only option was to pay the full amount using our credit card and seek reimbursement from our insurance company when we got back home. To their credit, the company reimbursed the full amount of the ambulance ride, the hospital charges, and the doctor's fees. So the moral is, if you don't purchase travel insurance when traveling out of the US, be sure your credit card carries a sufficient credit limit, and be sure to get copies of all receipts and medical records for the event for submission to your US insurance company.