Why are Canadian provinces' debt-to-GDP so much higher than the US? By the current account, the highest debt-to-GDP state in the US is NY, which is around 23%, with most states around 18%. By comparison, Canadian provinces tend to have much higher ratio, with Ontario at around 37% and Quebec over 40%. What accounts for this? Are the Canadian provinces responsible for distributing social benefits that would be under the federal jurisdiction in the US which skews up their %? Or are they just spending more irresponsibly than the US?
The Canadian provinces implement most of the welfare state programmes. The role of the Canadian Federal Government is to set out guidelines, and undertake fiscal transfers to allow provinces to stay near national standards. Since they have much larger budgets, they necessarily end up absorbing more of the economic cycle as being an automatic stabliser (i.e. they issue more debt).

There are no balanced budget laws for Canadian Provinces. American states generally have balanced budget rules, so debt levels are necessarily low. The states that do not have balanced budget laws are pretty much forced to follow the borrowing norms set by states with balanced budget rules.

Finally, the funding mechanism is different. Canadian city governments do not issue much debt, and there is very little project-based bond issuance. In other words, debt that shows up at the Provincial level ends up being financed otherwise in the United States (and does not show up in State level debt).