A better question would be what the US needs 11 carriers for, but hey...
I am cool with that - keep securing the sea lanes, build another hundred carriers if you wish, as long as you're the ones paying for it. It's just that what you described could easily be accomplished with about half the number of carriers you currently have.
Let's not pretend that carriers are about anything other than power projection. The US has 11 because they want to be in a lot of places. As such, I'm not sure how much you could cut without losing both the ability to rapidly deploy and rapidly deploy in force.
Consider the logistics that go into maintaining a ship like a super carrier. I'd be surprised if 2 weren't in dry dock at any given time: one ship per coast. If that's the case, then 4 ships are active in the Atlantic and 5 in the Pacific at any given point (the strike groups are split evenly between coasts with another being stationed in Japan). If you want to be able to deploy 2 to a troubled area, you need to have 3 carriers per coast (one is always under going maintenance). Of course now, if you only have 3 per coast, you have nothing in reserve -- see, US military doctrine requires the ability to wage two major wars at once, so you can't just borrow your Pacific fleet to deal with Libya.
Perhaps if the two-war doctrine were scrapped, and you could find a few countries like Japan willing to host a forward deployment of a nuclear-powered and nuclear-armed strike group, you could reduce the size of the USN's carrier fleet to 8. Or if you stopped with the power projection doctrine and went with a defence doctrine you could drop the number further.
As for countries of the size and power of France and Britain, 2 carriers are perfectly enough.
2 is a good number, yes. It allows for one to be operational at any given time and 2 to be operational quickly in case of war. Considering the down time a machine like a carrier undergoes, I don't see a point in having less than two.