The way they curb free speech, even projecting that internationally.
Their announced intention to become the world's superpower and displace the US militarily, technologically, and economically, and the risks to US interest which tie to that.
Their active pursuit to enact that claim, specifically with rapid military technology development, and international organization of BRICS.
Their aggressive tendencies towards US allies.
Their aggressive spying on US military and industrial facilities.
China has barely started with Taiwan. There are projections of China moving to forcibly take Taiwan within the next two years. It may be a bit later than that.
If the US doesn't take a strong stance in support of its ally in Taiwan, China will only take it sooner. Once China invades, that begins the massive expansion to WWIII that JP Morgan CEO claims has already begun with Ukraine.
The US can't lose Taiwan as an ally, strategically or economically. If we give up our support of Taiwan we've as good as handed over hegemony to China. And we'll have lost the AGI race in its infancy.
It depends on how long you're willing to roll back US interventionism. If you're talking about pre-WW1, maybe. But even by the mid-late 19th century the US started sticking its nose in the Pacific (which alarmed Japan, which contributed to that countries subsequent militarism). So I'd say you'd have to go back even further.
If not the US, it would probably be Europe and/or the Soviet Union. China and the Soviet Union nearly came to blows in the 60s.
Europe decolonized largely because Hitler wrecked major continental colonial powers France and the Netherlands) and put Britain with their backs against the wall such that it had to partially abandon its empire in order to defend itself and avoid a complete disaster. So they let India go, but tried to hold on elsewhere. This worked to some extent, but not in others. What remained tried to morph into the Commonwealth, this was only partially successful.
The US assumed the crown, this time with a different model, hegemony vs. colonialism. They had a rival in the Soviet Union, which funded Communist revolutions in many parts of the developing world. With the exception of Vietnam, something the Chinese did not do. They valued North Vietnam as a buffer against Wester imposition, but were not too keen on a reunified Vietnam, indeed they invaded a few years after South Vietnam collapsed.
The way they curb free speech, even projecting that internationally.
Their announced intention to become the world's superpower and displace the US militarily, technologically, and economically, and the risks to US interest which tie to that.
Their active pursuit to enact that claim, specifically with rapid military technology development, and international organization of BRICS.
Their aggressive tendencies towards US allies.
Their aggressive spying on US military and industrial facilities.