Blackstone
Brigadier
Since WW2, it's been the US and allied countries that have provided most of the security around the world's waterways, and China is a welcomed late comer. The UN has welcomed Beijing's involvement in piracy control and UN peacekeeping and want more of that. On the other side of the coin, China is only in the infancy of providing global maritime common goods, and at this point in time, it simply doesn't have the ability to provide much more.That is the responsibility of all navies not that of a single hegemon. And huge flattops have no significant role in that work.
The new Chinese islands will contribute more to fighting piracy in SCS than US FON actions.
There was never a single world-wide hegemon, because US is really a regional (Western Hemisphere) hegemon with a global alliance network. That system is coming to an end, and it's not clear who would step up. The situation resembles the period between WWI end to WWII start, when Great Britain ceded global leadership to the US, but it wasn't willing or capable to don the mantle and smoothly transition in its new role. China is trying to step up economicaly, as proven by Xi Jinping's speech at the World Economic Forum, but it's not clear if it's up to the task. Time will tell.