I'm sure there are Pros and Cons to absorbing Canada - some obvious, some actually requiring some thought.
Is there any support for the idea up there?
Doubtful.
However, I suppose the ONE Province in which such an idea might take hold would be Quebec.
There are enough French-speaking Separatists up there to make-a-go of the idea, I suppose.
After all... the latest 'movement' in Quebec to break away occurred well within Living Memory, as I recall.
Their best chance of breaking away would be for the Province of Quebec to apply for US Statehood.
And, once Quebec is gone, the floodgates might open in one or more other Provinces.
But even a separatist Quebec seems an unlikely prospect.
Besides... who wants a non-English -speaking State and out-of-synch culture to deal with?
It's probably best to leave Canada as-is unless we begin to pursue a North American Union of some kind.
An English-speaking Union.