We all know the US gov rules, dictate to rest of the world.
So if they cornered the btc market, afterwards the btc price could only go up, factor with this a few btc friendly directives, and a massive coup would have been achieved.
What is the downside?
Once the rest of the world starts to figure out what's happening (and there's guaranteed to be a leak somewhere), everyone else will dump, and the US Government will be 1 trillion short. Sure the gains
could be pretty massive, but is still disproportionate with the risks. Remember, it's the people's money they're spending.