Like China, I too would be concerned if the somehow-unarrested serial killer who lives down the street suddenly got access to enough explosives to level the nieghborhood
"The U.S. is peddling the China nuclear threat narrative, finding excuses to seek strategic advantage," a Chinese foreign ministry spokesperson said.
Later, same article
The U.S. has consistently pointed to China's expansive and growing nuclear weaponry. An annual report by the Pentagon last October said China had more than 500 operational nuclear warheads in its arsenal, and will probably have over 1,000 warheads by 2030.
What is China's serious concern, exactly? That the US is consistent about its appraisal, or that they're reacting cogently to it?
Probably that the US is reacting at all. With the knowledge of which country is the only one insane enough to use nuclear weapons on real human beings, and China having a no-first-use policy, it makes sense to be concerned when the country currently funding a genocide is making a nuclear strategy.
As yogthos puts it, "Everybody should be concerned about a rabid chimp with a hand grenade."
It's nukes, so of course - every time anyone makes a move it's stressful. That said, China is doubling its stockpile this decade and then calling foul just because the US is aware of it and discussing how it affects their position.
Regarding American willingness to strike first: The only US administration who has talked about using nukes in a casual way is Trump's. As to accusations of genocidal tendencies, neither nation has a clean record.
The concern is that the USA official stated policy is that they reserve the right to use nuclear weapons in a first strike, while China's official stated policy is that they will never use nuclear weapons in a first strike under any condition.
Actually I don't think the 1000 by 2030 is necessarily true.
China's nuclear strategy is minimum deterence because they learned very quickly that stockpiling like Russia was not a good idea.
I'm sure they're just mad about the USA doing anything, but I could see them being ticked off by the USA trying to force them into a nuclear arms race.
Also probably scared that the USA is going to dump a ton of money into things like hypersonics and LRAAMs again, which is probably the only two things China has a current advantage in lol.