That would mean likely the US nuking Iran in a fit of rage while the TV propaganda plays images of the sinking ship and wails and gnashes its teeth and demands action then applauds or falls solemnly silent when it happens. The media will simply say "well maybe it wasn't right BUT they did sink our carrier, they shouldn't have done that and we wouldn't have done this, you know how we are". And that will be that.

Russia is as someone else noted tied up in Ukraine and doesn't want to escalate with the guy (Trump) who can force Ukraine to sign a treaty or agreement with them. Getting into a hot war with the US would be a nightmarish strain on their military and bring them and US very close to nuclear war. Russia will resent losing its Iranian partners to the US but it won't end the world or Russia in order to attempt to stop it. China is uninterested in getting drawn into a war at all, much less that far from its shores where they don't have the advantage in logistics compared to the US and would be at an awful disadvantage. China's navy is not a deep blue water fleet like the US, their navy is structured around coastal defense in the South China Sea and it and their air force lack the range to engage in anything protracted with the US.