Knock out? no, best option is to have them all pre-hacked and send out spoofed data at the most desired times, especially if you knew what weapon systems were relying on them. Knocking out the satellites is like flipping the table in chess, you'd only do it if you were pretty sure you had no chance of winning because everyone else in the tournament won't like it. The duopoly-based cold war is over and those winner-take-all tactics were what drove USA policymakers to try so hard to get China to play on the world stage.