First, go read Tim Bray's post. What follows will make no sense without it. (I originally sent it as an email to Tim.)
Hey, wonderful! I'm all for it.
It got me to thinking about symbolism for the Federation. How 'bout we use the Maple Leaf Flag, but with the red bars changed to blue? This would keep the "red, white, and blue" symbolism important to Unitedstatesians, but the outline would be that of Canada's flag.
Then we could use America the Beautiful as the national anthem (far better than either official anthem both in lyrics and melody, in my opinion). I think verses 1, 2, 7, and 4 of the final 1913 version, in that order, are the keepers, and the blue bars in the new flag would resonate with "from sea to shining sea".
Politically, the Federation keeps a prime-ministerial system with an elected but ceremonial head of state, like all sensible democratic countries. We'd have 16 states, 10 provinces, 2 commonwealths (Massachusetts and Pennsylvania), 3 territories, and one free city (Washington City). We'd also of course have New York City, the financial capital of the planet Earth.
As for the Republic wanting access to the Pacific, let them buy a border province or two from Mexico. "How many Texans does it take to screw in a lightbulb?" "Texans don't screw in lightbulbs; they go to Mexico."
On a more serious note, this map is interesting. Back in 1981, a Washington Post writer named Joel Garreau (of Quebecker descent) wrote a fascinating book called The Nine Nations of North America, showing how the continent naturally fell into nine distinct regions (with a few outliers like Manhattan, D.C., and Hawai'i). There's a main web site where the whole book is available online; it's back in print, too.