Re the US fresh water concerns as Lake Mead and the Colorado river threaten to run dry, I could foresee this becoming a real flash point for future conflict between Canada and the US if the US sees no other viable path to getting fresh water if certain hypotheticals play out.
the hypothetical is that as areas in Canada's vast North, CONTINUE to become unlocked from the permafrost and give access to massive amounts more of fertile, resource rich, arable lands that people are happy to live on and exploit. Canada is going to get wealthier and wealthier, while the US suffers and struggles with the changes. I have seen models showing Toronto and Montreal, being more like Florida in temperatures and climate, and the vast far North of Canada being more like Edmonton was 20 years. Very liveable for those willing to deal with real winters.
Canada will continue to be able to absorb, and will need, mass amounts of immigrants and migrants to settle and live on and work these lands, and similar to how the West was settled in the frontier days of the US, that will be one of the biggest impacts of the planet warming.
Consider this population density map of Canada, but imagine a change where people are now willing to fill in most of that white, non lived area as it is not prohibitively cold and wintery.
Understand that
50% of Canadians live South of Seattle, in a very narrow corridor abutting the US border.
Now look at this US map...
... and imagine instead it is so hot and devoid of water and arable land that as was the case in Canada's north (but due to cold and permafrost), that the South and MIdwest of the US is no longer inhabitable for the masses due to heat and drought and lack of arable land.
The US population cannot all just shift up towards the Canadian border (as the Canadians have done due to winter) and instead those citizens would have to seek mass migration to these new Canadian frontiers and to become Canadian.
You would see Canada, effectively becoming the US and the US effectively becoming Canada in terms of populace and GDP.
Would the US allow that while they still had the strength to take action instead to just find a reason to absorb Canada as the 51 State, like it or not and thus still rule via elections and superior numbers and to then allow direct migration with incentives for those who move to the new US frontier?
I know how much this forum loves to play with these type of doom type scenarios (not) but Water Wars are a topic of Think Tanks and academics around the world, including in Canada where i have listened to many podcasts discussions theorizing what the US might, or might not due, if things get unliveable for them? For those who hate such speculative talk and think only once a real threat presents should it be discussed, feel free to skip this post with my blessing.
As Canada looks at an expanding and resource rich North, it would be foolish for gov't to not be considering the increasing challenges on our neighbours to the South. A good gov't is game theorying all options out and trying to find ways to navigate them all, if they present.