Whilst it's hard not to admire the commitment to defence shown by our American cousins the simple fact is can they afford it? Have a look at:
http://http://www.usdebtclock.org/
This website tracks US spending and debt, which currently stands at $17 trillion, a whopping $54 000 per citizen. Whilst it's nice to have a large set of the latest toys at some point they are going to have to reduce spending. Each carrier is $13 billion and they're building 11 of them.
Whilst the UK also has a hefty debt our government is trying to rein in spending, even if they're doing a pretty poor job of it.