This is silly. The US isn't trying to justify inaction, and cumulative contributions isn't useful for anything. Of course the United States' total emissions are higher--it industrialized nearly a century before China, long before climate science existed or before technology existed anywhere to reduce emissions.
The relevant metric is the rate of change of emission--are we putting more or less carbon into the atmosphere year over year, and by how much? China is continuing to increase its emissions year over year, while the US emissions are falling (though not quickly enough).
Another interesting metric is the consumptive emissions--how much emissions are generated from trade (e.g., when an American buys something produced in China, the carbon involved in manufacturing that item is emitted in China, but the American benefits from the pollution as well). I actually expected the US to have much higher consumptive emissions relative to China, but it looks like the consumptive emissions pretty closely track the productive emissions while being just a bit higher at 5.77 billion t/yr (falling gradually since 2005), while China's are at 9.86 billion t/yr and climbing.
On the note of consumptive emissions, the United States should not only implement its own carbon pricing scheme, but it (along with other rich countries) should also implement a border adjustment so countries like China don't enjoy unfair competitive advantages because they pollute. This would incentivize China to reduce its Co2 or suffer heavy economic losses. It would also increase manufacturing in countries that are more responsible.
That said, to your point, the Democratic Party pays lip service to environmental concerns (the current $3.5 T budget bill is making expensive token gestures to the environment which will cost polluters virtually nothing) and the Republican Party isn't even doing that. So yes, America has a lot of room for improvement (but at least America isn't arguing that we should be allowed to increase our emissions, contrary to Chinese arguments).