The US may be our friend but they still have a "Manifest Destiny" to occupy the entire North American continent. However, in regard to Canada, instead of expending resources invading, they are content to assimilate our culture quietly through their state controlled media, business mergers and US products.
This wishlist is just another "Borg implant to assimilate us into their collective."(sorry non-Trekkie's, but the analogy fits fits like a glove). I agree that on the surface it is political maneuvering towards better cross border relations, but keep in mind that politics is a chess game, every move is strategic.
And if you study history there is one common denominator,
Empires expand and then eventually Fall. It may take centuries, but the US will be no different.