How does an increase in US oil supply not affect the global price of oil? Increases or decreases in OPEC supply decrease or increase the global price. The US is significantly engaged in the global oil market, we import about as much as we produce. Increasing our domestic production decreases our draw on the global supply.
Future Asian demand and Russian supply are the big factors.
The US already produces more oil as Russia.
Expanded North American reserves would have a military value in the event of a world war that denies the U.S. access to oil beyond its shores
Reserves are not production rates. Oil in the ground does not match oil flowing to the refinery. See Venezuela for a great example.
You have a valid point that proven reserves of oil in bitumen form are not militarily significant, unless they are being produced. It's not just a matter of drilling some development wells. I think that military concerns are based on a remote possibility.