> the U.S. Navy has guaranteed free navigation
The sea has never belonged to anyone but this statement implies that the US has ownership rights with regards to ocean usage that they now let others use at their whim.
The only word I can use to describe that is hubris
However on the open sea, there is no such authority. What's to stop someone from sailing up and seizing your crew and cargo? You don't know the nationality of these pirates, and even if you did you have no way of forcing their government to do anything about it. Indeed they may be working for that government. You could try to defend yourself, but then the pirates will just better arm themselves and the odds of violence escalating dramatically increases.
Someone needs to prevent piracy and unlawful seizure for international shipping to be possible at its current scale. Having a single power guarantee free navigation allows ships to cross the world while avoiding complicated jurisdiction divides (if one nation won't give you permission to sail through its waters, you can go around) and eliminates jurisdictional overlap (Country A says Country B's ship is committing piracy and vice versa) which could lead to conflict. It's also just more efficient as the vast majority of nations don't need to duplicate the infrastructure to maintain a navy that can protect assets on the other side of the world - which also means countries don't need to enter arms races to protect themselves from their neighbors' defensive fleets "just in case" they aren't really that defensive.
> Having a single power guarantee free navigation allows ships to cross the world while avoiding complicated jurisdiction divides
So the rest of us are to assume the US taxpayer and their government are acting in good faith? nothing in return for having all those ships and men out there for months at a time? Whats the cost to the US for protecting assets from Guinea-Bissau?
> Someone needs to prevent piracy and unlawful seizure for international shipping to be possible at its current scale
I don't think you get the gist of my argument. To put it simply, to whom does the US account in their capacity as police of international waters?
Who said the US must be that 'someone'? Even the UN - if we won't kid ourselves is a US institution - might have been acceptable. A single power's whims are to be trusted for what reason? How do we know they wont collaborate with Pirates and other bad actors? Who will bring them to book or answer questions?
In practice the US has such an immense navy that while it guarantees free navigation there is no real need for other nations to, and if it were to oppose free navigation there is no navy that could stop it, so at the moment the US de facto decides if free navigation is guaranteed, but there is nothing de jure entrenching the US in that position - should it ever derelict its duties or otherwise grow weak there is nothing stopping another nation, or group of nations, from taking up the mantle.
On the other hand if an international body were to be set up to do the job, then we become totally reliant on its efficacy. It's impossible to have a truly independent organization - the people who compose it, as well as the people who provide material resources to it, are not independent and unbiased - and unlike a nation which benefits from the trade it protects, this organization's only incentive would be to appease its backers. Even if it avoided malicious corruption, it would fundamentally entrench the geopolitical status quo, and getting everyone to agree to remove it may be impossible even if it strays woefully far from its mission.
The US's position may rub a lot of people the wrong way, they see the US as being some sort of self-appointed overlord and fear if it has nefarious intent. They fail to realize the level of gross indifference that the US has towards the larger world. We just want to be able to import cheap crap, any benefit to other nations is purely ancillary, and we will continue on our course for precisely as long as it is the easiest way of maintaining our steady supply of cheap crap.
