How about the ancient technology of the separate cold/boiling hot water pipes? I'm not an american, but that's the most odd thing I find about the UK.
[And yes, I know that we have crazy plugs because of our strange ways of wiring up houses. However, of all the places I've been the US has by far the worst plugs.]
1) It's not that common any more except in older buildings.
2) Historically, this was because only cold water was deemed potable because it came directly from the mains supply, whereas hot water would be lying around heating tanks etc. and might be contaminated. So by keeping them separate, you always knew the cold water tap was safe to drink from.
Thanks!