That east coast stuff is all fine and dandy, but about 10-12 years ago a Canadian war plan, derived during the depression era,came to light. It involved invading down the Red River valley area of Minnesota/North Dakota hooking east go to then north up the Miissippi/St Croix river valleys taking the Twin Cities and finally taking Duluth. and then to defend/hold it till the US gave in on whatever the Canadians wanted.
This does have the advantage of not trying to cross the St Lawerence waterway....and seizing some of the grain belt, although from what I understand the grain production capabilities during that time line are greatly lessened from drought and Nuke winter.