What was the reasoning for gas-turbines instead of nuclear power? I don't relly get that one. 
Money, simplicity, ease of repair and replacement. When you have a dozen supercarriers having one or two down for a nuclear fuel replenishment cycle, which I believe is at least 6 mos, isnt that big a deal. But when you have only one or two, and one is down, it can lose a war for you. Additionally nuclear reactors need a huge training and support mechanism in place for them. And is it worth it for just one or two? Yes the Brits have submarines with nuclear reactors but I'm sure they are of a different type. Gas turbines are much simpler, cost less, and are very efficient nowadays.
America has the worlds only truly "Global Navy" and nuclear is the way to go for us. We have to move huge carriers across all the worlds oceans and we often have to do it quickly. Britain, while also having global responsibilities, doesnt have the same mission for their navy.
Yes its true fueling gas turbines is expensive as well but only if you move the CV across large distances. Crews can train in home waters, or even while docked, and patrols can be done at economical speeds.
Dont forget we also have carriers that use standard propulsion in our Tawara and Wasp class Amphib assualt carriers. We have a follow on class planned and all operate the same STVOL aircraft the Brits do, AND, will fly the same F-35 variant as well. We have 13 of these LHAs and LHDs, both types being in the 40,000 ton class. One of these ships continuously sortied 20 Harrier jets during the Gulf War so they are legitimate aircraft carriers in their own right. So really America has 24 carriers with over 1/2 powered by Gas turbines. All the other CV players in the world are conventionally powered as well. It would have surprised me had the RN said they preferred nuclear power instead.
