I have both a US wired keyboard and a UK one sitting in front of me as I type (I prefer the US as I have used this layout for years but recently moved to the UK so my new Mac came with the British keyboard. I bought a US keyboard on a trip the the US.)
So the differences are:
1. Function Keys - Identical
2. 2nd row, Left key US is ~ and ~ where as British is +_
3. 2 key shift Euro symbol
4. 3 key shift has UK pound key not #
5. On the rhs of the QWERTY row, US has \| UK has an extended return key
6. On rhs of ASDF row, US has return, UK has \| and then a smaller return key
7. On the lhs of the ZXCV row, US has a larger shift key, UK has `~ key
8. On the rhs under the f13 to f15 keys the US Keys are labeled fn home page up
UK have arrow symbols but behave the same.
I really prefer the US as it has the extended shift keys symetrically on both sides, the UK one is only on the RHS.
That is all.
Dave
Dave