and thats good enough. basically it makes the US ask if it wants to sacrifice 20 of its largest cities for japan over some uninhabited islands in the ocean, if a shooting war with japan happens i doubt the US would want to join despite its statements, for one, generally only chinese civilian ships are in the disputed areas and they are hardly armed. if a war starts it would have been japan that started it, making it extremely hard for the US to support japan. and even if the US joins, it may not change much, china can just sit and lob ASMs at the area, unless the US wants to fight a land war in china, against china, there is little it can do from a military stand point. china has no need nor wish to attack the US mainland conventionally, its pointless and probably nuclear at the end of it anyways. what china cares about is its near seas and claimed territories, its claims are clear and have not changed for its entire 64 years as the PRC and it has made clear that taiwan independence is not up for negotiation even if the US was to state it would go nuclear for taiwan, china would still not hesitate to fight, it favors one on one negotiation with respect to other disputes but has shown that it is unafraid to fight for them if necessary.
the chinese know time is on their side. at current growth rate, or even lower, china will match then exceed US GDP in less than 20 years and military modernization would be more or less completed, by then it may not matter whether the US joins a local/limited war in the near seas or not. hence there is nothing the chinese would like more that peace atm(barring everyone giving them what ever they want of course)