Agreed self-sufficiency isn't the best term.
But if I were to rephrase it, let say that self-sufficiency in terms of the quality of life - US would be in much better shape than Canada. Canada has _significantly_ much more to lose than the US.
The biggest 'enemy' of Canada is not America(s). It's the Canadian govt itself. Most Canadians cave into their tribal instinct of 'us versus them' and cannot see past that own manipulative govt.
Canada has not only proportionately significantly more trade restrictions (between countries) compare to US, but it also have significant restrictions to trade and free market within Canada: example quotas on milk, dairy, beef and chicken. There are more taxes at every stage of a transaction with little benefits ( yes people mention 'free' health care but it's another subject). Relatively unaffordable housing mostly due to taxation (For example the tax part of condo in Toronto/Vancouver is cumulatively about 35%) etc.
Just to be clear both govts of US and Canada are tyrannical. Americans on an average distrust their govt more than Canadians - hence they overall do better in keeping their govt overreach in check.