Well this is almost a VS topic, but lets set the record here.
Everyone is telling about the French and the UK in the ancient times but what about the Dutch who owned the seas for nearly 200 years (Next to the UK)
Or the Spanish before that? So if history is going to be a part of this then lets make sure that it is a correct one, as back then the Spanish where by far the biggest armada in the world, and it took a painful alliance between Rival Netherlands and Great Britain to destroy it, which eventually back stabbed the UK as it enabled the French to become a significant naval power (Spain was keeping them in check)
So some historians argue that the defeat of the Spanish armada was the start of the defeat in the north US territories.
There was no way that the British could fight France on the land and the Dutch on the seas and be succesfull as history books concluded.
That being said, as for China today for most it sounds ridiculous that China is building up a massive fleet and army, but on the other hand the US is changing its policy to "contain" China, while China on the other hands wants to stop US influence in the region so that it does not come any closer then it already is.
So from a Chinese POV its going to take ALOT to achieve this.
And the one and only way for the Chinese without starting a war is to deter its neighbors and indirect the US and by being a pain in the *peep* at the UN.
As for the USN being the most powerful navy and biggest i have to agree in paper you guys are in size and overall capabilities the best.
But taking on the whole world?
During the Cold war there where various models to simulate a war between east and west, and it was recognized that on both sides that the USSR and Its allies (Warschauw pact) would outnumber the west 3 to 1 and that on land and sea the west was not as effective as they would think they are given the technological differences between west and east, not to mention that the USSR outnumbered the land forces by nearly 10 to 1.
My point here is that even today while the USN is the biggest top dog around it has significant problems in a attempt to take on the rest.
What most people seem to forget that most allies of the US itself have better frigates and destroyers individually.
Stealth, Automation, Battlefield awareness and high precision LR and SR weapons are not just a USN feature. Today most respectable nations field these techs in their small but very capable navies and some have better frigates and individual ships then any USN surface asset around.
The bulk of the US power comes from 5 aspects:
1: A superior Air force
2: Its carrier groups
3: Its Nuclear Subs / ICBMS
4: Its economy and geographical access to regions
5: Its Intel gathering and exp to field Intel into strategy.
These are the 5 primary assets that the US has, and for this i did not list the regular army as they are GREAT on paper bu in the RL world it can be decimated rather quickly as "the rest of the world" is just WAY above anything the army can accomplish.
(Sure people will argue about it if i am right or not but bare with me)
I listed 5 things as general idea to lay out a battle between US and the rest.
I venture to say that in a war the USN and the US Military machine is by far the biggest beast around, but anyone even thinking that the US would be able to overcome "the rest" regardless if this is on Land, Sea or Air is suffering a mental meltdown.
And i personally say this the amount of Havoc that the US is able to create world wide in a all out war would make every war in history look like a joke.
But it will be brought to a stop and eventually being beaten at the battle field, and eventually in its own backyard and mainland.
Keep in mind one of the most important assets the US has is its global reach and its bases world wide.
If those are being taken out it would severely weaken the US and would force it into retreat. Where the rest of the world can literally starve the US into submission.
And i do not want to hurt anyones feelings or disrespect anyone here, but if the US would attempt such a thing, it would make the same principal mistake as Japan, when they attacked the US, as Hitler when he attacked USSR while fighting the rest.
It would awaken a world wide beast.
Besides that the world would a far lesser place without the US, but on the flip side the US would be nothing without the rest of the world.
Conclusion we need each other to much, now if you want to create a "world ending event" then a war between US and the rest would be a pretty darn good point to start lol.