n0m, her uf hacken a chainik. The posuk says very clearly why one should not curse a king or a rich man — because you will get caught. No other reason. It has nothing to do with respect or society. Since when is a rich man a leader? The ONLY reason is that you will get caught and they will punish you. In our society that is impossible; Trump neither can nor would punish anyone for cursing him. Therefore there is no reason not to, except that he doesn’t deserve it.
And the king being the state is the very DEFINITION of kingdom. There is no kingdom without the king. Again, stop hacking a chainik, it’s like you’re demanding proof that a dog is not an elephant, or that a rock is not a tree. They are very different things.