and apart from George W most Presidents haven't been anywhere near as threatening as say North Korea's leaders, or a rogue Islamic insurgent with a dirty bomb, virus, they have the ability to wipe out millions, maybe billions in moments. Obama won't push a nuclear button - and neither would Putin, but he will roll over on this neighbours, a show of force,
as to China, they are as tightly controlled as North Korea, the people have little or no freedom, and any kind of dissent is met with untold force of arms, and are killed, or interned for good for their pains.