Here's an odd challenge for you fine folks.
With a POD of 1900, make the US-Canada border come to represent the same thing as the South Korean/North Korean border, complete with Canada as a dystopian Orwellian dictatorship. The more colorful the better.
In OTL, the US-Canada border is one of the world's most peaceful - make it personify as much of a divide between tyranny and freedom as the Iron Curtain or the 38th Parallel.