I guess USA would have no problem with some other country making a movie where the heroes had to help assassinate the American president. The truth are that the movie is very bad taste, and comparing to usual North Korean rhetoric, it was more or less what you could expect.
It's not at all bad taste. What's bad taste is North Korea. I guess you approve of terrorizing your own people for decades. In any other country, it would not at all have been acceptable, at the very least not for any longer than a few months or years. Yet since it's North Korea, we seem to have accepted it. What's been going on constantly in North Korea (without the world apparently caring too much) is arguebly the worst thing (very basic human right injustices, no civil liberties, constant brainwashing & living on the brink of death/deadly hunger, as well as the famous work/death camps) the world has seen since World War 2.
The North Korean regime are monstrous, but that's no reason to be rude to them. If there live a psychopathic lunatic in the neighbourhood, I don't insult them, I call the cops on them.