[BB_TX]

It does seem Medicare will cover you traveling thru Canada. You would have to ask about your supplemental.

When does Medicare cover health care services in a
foreign hospital?
There are 3 situations when Medicare may pay for certain types of health care services you get in a foreign hospital (a hospital outside the U.S.):
1. You’re in the U.S. when you have a medical emergency, and the foreign hospital is closer than the nearest U.S. hospital that can treat your illness or injury.
2. You’re traveling through Canada without unreasonable delay by the most direct route between Alaska and another state when a medical emergency occurs, and the Canadian hospital is closer than the nearest U.S. hospital that can treat your illness or injury. Medicare determines what qualifies as “without unreasonable delay” on a case-by-case basis.
3. You live in the U.S. and the foreign hospital is closer to your home than the nearest U.S. hospital that can treat your medical condition, regardless of whether it’s an emergency.
Remember, in these situations, Medicare will pay only for the Medicare-

From:

https://www.medicare.gov/Pubs/pdf/11...ted-States.pdf