The nuance and significance might be that Russia is actively seizing another sovereign nation's territory, whereas the US is not.
Sure, they bluster. But that would be really stupid. "You said something I don't like, so I'm going to kill us both" level of stupid. China talks tough, but I don't think they're actually that stupid.
The US walks a line on Taiwan that falls far short of actual support for One China but does enough to support it that the US has a lot of room to escalate with China if the US wants to without starting WW3.
It's a real cluster fuck.