If China can only destroy the planet once with its weapons is that less concerning than the US and Russia who can destroy the planet many times over?
Plus I'd be astonished if the Chinese don't have more capability than they admit or the US is even aware of.
Plus if a smaller power is convinced, because of Trump's erratic behaviour, that the US will attack, they may strike first, even against overwhelming power, because they perceive it as their only choice.