One of the differences that strikes me on here is the difference in attitudes to pregnancy and birth. In the UK a lot of women will still drink tea/coffee, have the occasional glass of wine etc. Whereas in the US they seem to give it all up. With birth, it is so medicalised that it's (in my eyes) awful. I believe there are still some states where it is illegal to be a midwife. Here, most births are midwife led and there is support (usually) for home births etc.
Another thing that I think a lot of British people struggle to understand, is the power of God and religion in the US. We thought it was strange when Tony Blair was open about his belief in God and went to church. In the UK religion and belief is seen as a private thing, whereas in the US every politician and his aunt wears his religion on his sleeve and often speaks about his belief.
Oh, and what's the deal with American's hugging? I have relatives from the US that come over from time to time, (and I've met other Americans that do the same) and they just seem to hug everyone. I barely hug my OH, I never hug my mum or brothers and sisters, yet these people that I have never met just come up and hug me without care lol.
Another bug bear is when people say London, England or Perth, Australia. I realise there are Londons and Perths in the US but surely when you're talking about going to the UK anyway you don't need to clarify the country again.
Oh and I call the kitchen counter a bunker as well lol