Is Hollywood a real threat to China's culture and Communist Party?

Heard of V for Vendetta?

It’s not as big a threat as it was 30 years ago when China was struggling. But it is still a threat because the Chinese would see that freedoms are more prevalent and that the living standard is much higher. As the Chinese have become more open and traveled more, they are more aware of such things, but information is still highly restricted, and the bounty of consumer goods still attributed to the power of the State.

The Western culture is very pervasive. Hollywood movies are very attractive to other cultures.

Not as big a threat as reality is. Even the Chinese government is in favor of diluting its ideological purity these days.

History has shown us that complete isolation is crucial in controlling the masses. This is why religious sects are often swept away to a deserted place by their leader(s) and communication to or from the outside world is discouraged. Did you know that there wasn’t even television in South Africa during apartheid? I think they finally got it in the late 1970’s. But history has also shown us that no dictator or religious leader can keep the people down forever. China would be wise to relax their grip on the people willingly, even if gradually, because their people already know of the freedoms and higher living standards in other parts of the world.

Chinese culture dates the West by millenia. I doubt that it is under much of a threat.
Any Communist party, anywhere, is in a day to day state of jeopardy, and any threat to its’ existence is morally good.