For the record, there are other multi-ocean navies: russia, south africa, australia, canada, and argentina among them. I think that's a pretty small factor compared to the influence of the military industrial complex.
The size of the US navy dwarfs every other country considerably, even when factoring in oceanic boundaries.
The US has about half the world's aircraft carriers. Each aircraft carrier basically needs a battle group to protect it. The approach is indicative of the US's strategy: be able to have a few aircraft carriers anywhere important in the world, ready to quickly react to a crisis without sacrificing protection elsewhere. Since no other nation with aircraft carriers has more than 2 (and most have only one), that basically guarantees significant air and naval power anywhere.
The parent post doesn't mean the same thing you mean. The USN patrols every major seaway in the world; I sure don't see South Africa doing the same, nor Canada, Australia, The Russian Federation, and definitely not Argentina.
If the gp meant that, then the US would have a 4 ocean navy. I'm not arguing the size is the biggest, I'm arguing that the reason it is the biggest is not due to coastlines on two oceans.
And the US does have a multi-ocean Navy, divided up into 6 fleets that are assigned to certain oceans/seas. And its size is clearly due to the role it's been assigned by the US government. In fact, reasonable arguments can be made that the USN is too small for what it's been tasked with.
The size of the US navy dwarfs every other country considerably, even when factoring in oceanic boundaries.
http://en.wikipedia.org/wiki/Number_of_warships_in_service_w...
http://en.wikipedia.org/wiki/List_of_countries_bordering_on_...