Exactly, and I doubt the records are accurate and consistent across countries
Lots of people die while on the waiting list for a compatible heart or lung. In fact, these lists are prioritized on several factors, such as probability of success, age of the recipient etc.
And I don't know how hospice difference between the US and Canada, both policy-wise and socially. I believe that under Medicare, there are liberal hospice rules, enabling lots of services for comfort and quality of life, but when entering hospice, one must renounce major procedures like transplants and other surgeries. A person can remain on hospice a long time, as Jimmy Carter did. It is not just for the last few weeks of life. However, this also means that a person who has entered hospice will not be considered waiting for medical treatment. Does Canada have the same system, or would their numbers be counted differently.
In the US, about half the people who die while under Medicare use hospice benefits, That's a big number that could easily explain numerical differences between the US and other countries.