In China (and most east-asian cultures), you never disrespect rulers. It simply is not done, and they see it as a grave insult to the entire nation to do so.
In west-european and north-american cultures, particularly the US, everyone is a fair target for mockery. We mock Kim Jong-eun because he does things worth making fun of. We mocked Hitler because he did things worth making fun of, and we continue to do so. We also mocked Obama, Bush, Clinton... we still regularly mock Nixon, just because it's still funny. Britain makes fun of Cameron, and to a lesser extent, the Royal Family. We have entire industries based around making a mockery of our political leaders, and we would be insulted if you asked us to stop.
The only ones we do not mock are those who do absolutely nothing and are of no significance whatsoever. It would be a greater insult for us to NOT satirize them, because that says we don't give a single shit about them, that they are not even worthy of our derision.