Perhaps they ought to give the US State Department moderation control (to suspend) of the handles for heads of state?

Does that sound like a good idea? No? Oh, but if Twitter does it, then it's good, even if they know nothing of what the State Department knows?

You seem to be very confused about the differences between what governments have the power to do and what companies and individuals have the power to do.

The default position in the US and many other nations is that governments have no power except that which is conferred to them by a constitution (i.e. default deny). Meanwhile, the people have freedom subject to laws restricting their behavior (i.e. default allow). This means Twitter, Facebook, etc. can restrict speech on their platforms in ways governments often cannot, in the absence of laws that compel them not to. And in any event, such laws may well be unconstitutional.