At the center of U.S. Pacific region policy is its relationship with Taiwan, and the imminent threat for decades by China to conquer Taiwan. China literally runs military air and naval exercises to do so every day.
Certainly, if China felt they could get away with it and decisively win, they would invade Taiwan today. There are elements within the Chinese government and military leadership who are eager for war, and not just with Taiwan, but with the United States itself. There are others in China's government who prefer to play the long game, that over 10 or 20 years China will grow exponentially more both economically and militarily, while the U.S. and its Pacific alliances will weaken or completely dissolve, in which case China can achieve the same victory without firing a single shot.
And China's aggression with Taiwan, with Hong Kong, with outright genocide within Hong Kong, within Tibet, and within Xinxiang province against an estimated 2 million Uyghurs. And its recent expansion into Afghanistan, and revealed advance support and training of a Taliban takeover, its aggression in the South China Sea against Taiwan, Vietnam, Malaysia, Japan and the Phillipines, its border aggression against India and Nepal, its across the board aggression demonstrates the threat China poses not just to the Pacific region, but to the entire world. And the level of overwhelming hostility and genocide they would impose on any vassal state or region, to insure no opposition will be permitted, or even permitted to live.
