Boy, I don’t know about that BC prong, lot of very high, young and jagged mountains plus a really thick woods. Let’s see some battles soon.
I agree. Shift the invasion to the MacKenzie River Delta and the Alaskan North Slope and then advance down the MacKenzie Highway to the Great Slave and Great Bear Lakes region. Then on through the Canadian Shield hills, taiga and boreal forests until reaching the northern edge of the Great Prairies. After that it’s easier manoeuvring all the way to New Orleans and Texas (Yes Jack, we’re coming for you!). Along the way branch west and east to take transportation infrastructure, energy resources and the few limited population centres until the prairies. Limited invasions a la Norway, 1940, along the Alaskan coast and the BC coast and the seizure of Vancouver Island as an off-shore vesting and forward operating base to interdict North American military responses might be advisable too. Leave the big urban population centres around Vancouver and the Seatle-Portland region alone and bomb the crap out of them to trigger huge refugee crises which North American authorities will have to divert time, energy and resources to mitigating.
None of this is really feasible for anyone pull off if North American military and economic infrastructure is not completely shattered but some options are better than others.