I remember seeing an old poll on annexation conducted in ~2002 or so, and it had 15% of people or so in support, with Quebec actually being more supportive than the rest of the country, if marginally so. I'm assuming we are handwaving opposition to annexation here in order for it to happen.
The GOP would shift left or collapse and be replaced by a new center-right party, or challenged by a Constitution/Heritage-like party on the right. The Dems would shift futher left than most would expect-- think just to the right of Bernie Sanders-- but thanks to the American electoral system an NDP analogue would not be able to go far.
The interesting question is how this affects the former provinces' governments. Would they switch to a directly elected executive or just adopt a South African-style head of state elected by the legislature.
There's nothing that explicitly blocks states having parliamentary systems in the US constitution, no?
