From a strictly objective view of history and human nature, you worry about any nation that becomes disproportionately powerful. Plenty of examples.
Athens was democratic yet devolved into an Empire exploiting the threat of the Persians in order to rule the other city states until they rose up against Athens, causing Athens to lose its power due to over-extension and overspending in the effort to try to sustain the empire.
Romans started as a Republic, ended up as a totalitarian empire.
Etc. Etc.
But at this point, China's power is vastly over-rated. They have a nuclear deterrent and enough teeth to give problems to anyone who would attack or invade China but they have no capacity to project globally, or sustain any large scale overseas deployment.
The biggest power/leverage they have is economic and we handed that to them. The can financially hoist the U.S. on its own petard by simply electing not to lend any more money to the US government.
Whose ides was this, to put the entire U.S. economy at the mercy of a foreign banker? Look in Washington and New York. Look in the mirror.
I'm not worried about China attacking the US at all. The more likely scenario is that China continues to use its economic power to press down different paths in its global economic relationships influenced by "Asian values" -- that China does deals of all kinds in places where we are used to having a trade and finance monopoly.
That China provides competition.
People don't like competition. They only talk up its benefits when they are winning.
Economic competition throughout history leads to war. Follow the money. That's the scenario I see as likely. But despite the underlying economic competitioin, the rhetoric will be about "freedom" and "human rights" etc. etc. The model is well established.
China isn't interested in conquering the US or taking away our Constitution. What I think you are worried about is that this country willingly relinquished full freedom of action through fiscal profligacy. When your banker owns you, your freedom of action is gone.
And China is our banker.