Birdsong: Now, I do hear birds singing in the US, but it's typically just a couple, and just not the sheer diversity. At one end of an avian migration route, the UK simply has more birds, mostly coming to the UK to breed, besides residents. Plus the work of the Royal Society of the Protection of Birds has helped conserve the variety, unlike in the US where many native species have been decimated. I also like seeing the ubiquitous magpies flying about, and in the colder months the sounds of rooks and crows "cawing" in fields.
Religious tolerance & liberal values: America likes to think of itself as the "land of the free" and a cultural melting pot. It isn't. Seriously, the way religion has such a stranglehold on American politics would be considered abhorrent in the UK which has a much more "live and let live" mentality. Also the political values in the UK are such that even the Conservative party, the most right wing of the three main parties, is to the left of the Democratic party. Talking to students her about the US healthcare system and the reaction against "Obamacare" they just couldn't believe that the public would be against universal health care and, especially, that people could be denied the best possible health care just because of what insurance (if at all) they had - they considered it just so morally alien to them. They consider that access to the best possible health care as a fundamental moral right for everyone. And don't get me started about access for all to university education.
Proper tea: None of this weak namby-pamby weak Liptons rubbish that you get in the states. Good strong PG Tips or Tetley tea. What the Brits call "builders tea".
Sense of humor: I must have a caveat here that most of my friends have a sense of humor where they get sarcasm, double or "single entendres" and more surreal "pythonesque" (which I discovered is actually in the Oxford English dictionary - humor or situations that recall Monty Python) jokes. But too often Americans don't.
The joy of snacks: Although the UK has a bad reputation for cooking, it really isn't deserved. In the past couple of decades the British have become obsessed with cooking. Just look at the popular cooking TV shows in the US like top chef, most were stolen from the Brits. Even your average pub prides itself on the quality and variety of its dishes- as opposed to burgers, fries and nachos that you find in nearly every US bar. The restaurants are also typically very friendly to those with dietary needs - almost everywhere has a large selection of gluten-free, halal and vegetarian/vegan dishes. But, for me it's the snacks I really miss: salt and vinegar square crisps, Worcestershire sauce-flavored crisps, veggies pasties, chocolate digestive biscuits, custard creams (also a biscuit), and chocolate - Hershey's chocolate officially is not chocolate in Europe because of its inferior chocolateyness, snacks like Cadbury's flake and double deckers just kick the butt of American chocolatey snacks. Also a special shout out is warranted for the spicy deliciousness of HP sauce and branston pickle (the latter brings out the flavor of cheese in a simply mouthwatering way) … mmmmmmm.
What I don’t miss: grey skies and rain, rain, rain and more rain … sigh.