China...nothing compared to Rome? Puh-leeze. They were at least equal, and the Chinese were far more interested in the Romans than the Romans were in them. The Chinese had a variety of powerful enemies, and what is called "China" today was built out of bloody wars of conquest followed by cultural assimilation and suppression of the conquered peoples. China typically exerted great influence throughout Asia and even into the middle east at times. Also unlike Rome(and every other ancient civilization) it still possesses its ethnic, cultural, and linguistic identity. The Chinese invented gunpowder, crossbows, paper, and the mechanisms that power clocks, among many other things, and they also figured out an effective system for determining where an earthquake occurred at the moment it happened. This system was so accurate and precise, the Chinese immediately sent aid in the direction indicated, without waiting for confirmation.
China's history is rife with internecine conflict and bloody fighting with the locals(whose conquest was decidedly difficult and not terribly tempting because China was already huge.) Yet they were very often the most advanced civilization on the planet, and wealthy too, considering they cowed their neighbors into paying regular tribute. China until about the middle of the Ming dynasty was a very active power, setting up colonies in places like Taiwan and southeast Asia, mounting expeditions as far as Africa(and generously recognizing the local rulers as "governors" in the Chinese emperor's stead. This attitude is why we should be happy the Chinese and the Romans never actually met, for likely egos on both sides would be sorely bruised and Parthia could've been a bloody battleground) and intervening regularly in the affairs of surrounding states(Korea was and, apparently, still is, their favorite.) China ruled as much of Asia as Rome ruled Europe. It seems Rome gets a pass for being western and ancient, but China is judged solely on its attitudes under the rule of the isolationist Ming and Qing/Manchu dynasties.
As for Eastern Europe, it most certainly is underrepresented. Oh, and Prussia and Austria, for all intents and purposes, are German, in the same way the HRE is German. There would be no Austria today if Austria had united the German peoples under her rule, only Germany and Prussia