In the year 2066 in the Fallout universe, Anchorage, Alaska became on of the few remaining places on earth that still had valuable oil reserves. Because of this, China invaded Alaska -- and thus began the Sino-American war.
Of course, with Canada being stuck between a Chinese-invaded Alaska and the oil-hungry United States, one can only imagine that tensions were high between these once-friendly allied nations.
By February 2075, Canada agreed to be annexed by the US, thus allowing the North American continent to be unified under one government. Together, they were a sovereign nation gearing up to fight the Chinese and take back Alaska for their own.
But many Canadians weren't exactly happy about this, and a resistance formed to try and stop it. Let's just say that it didn't end well.
Because of all this wonderful Fallout history, the Great White North could be an incredible location for modders to explore and expand upon within Fallout 4. Perhaps we could even see a pre-war mod which explores the events of the Canadian resistance against the US. Alternatively, we could see what a snow-covered Canadian wasteland might look like in 2287.
Side Note: If you have a specific itch for a snowy wasteland, then be sure to check out the upcoming Fallout: The Frontier mod, which is set in a nuclear winterized version of Portland, Oregon during the events of Fallout: New Vegas and the war between the NCR and Legion.