Don't worry about pissing anyone off, Britain is a multicultural society, tourists are most welcomed, enjoy your stay and if your in London, take care with your wallet, there's a lot of pick-pocket thieves around, keep your cash hidden from view especially in busy area's. To see the sights, take a tour bus, If you get lost, don't hesitate to ask someone for directions, most people are friendly, If your driving, drive on the left side of the road, be sure to read up on UK road signs and try and plan your day. Most importantly, have a good time. Enjoy your vacation.
The fact you are asking the question means you are unlikely to have any problems.
Don't wear shorts or visible white socks in Europe unless you are engaged in an athletic activity. Don't wear Hawaiian shirts or any other overly casual clothing. Don't say things like "How much is that in real money?", "This burger isn't as good as at home.", or "You can't arrest me - I''m an American!". Avoid conversations about religion or politics unless you know the other person. Don't assume the other person approves of US foreign policy (even under Obama).
Tips:
You need a passport. You apply at the post office.
http://travel.state.gov/content/passport...
There are travel guides for the UK. Read them.
Dress comfortably for the flight to the UK but NOT shabbily. The equivalent of a polo shirt and khaki trousers is good.
Call your USA cellular provider and set up your phone so it works in Europe. Ask about the per minute cost so you know. Use Skype to call home unless you can use your cellphone really cheaply.
Take your USA driving license/state ID card (and school ID if you have one) in addition to your passport. If you have a school ID it will be valid for student discounts.
Call any credit/debit card issuers a week before you leave home to advise them you will use the card(s) in Europe.
Scan the photo page of your passport and the fronts of your driving license & school ID, and the fronts & backs of all credit/debit cards. Send the images to yourself by e-mail and keep them. That way you have access to the info via any computer connected to the Internet in case something is lost or stolen.
Print all of your airline itineraries and hotel/hostel reservations and keep the copies in your carry on. Keep the itineraries and reservations in your e-mail (don't delete them).
Check with your health insurance to find out if it covers you outside the USA and pays for medical evacuation to home (should that be necessary). If yes then take proof of coverage with you. If no or not sure then get trip medical insurance, which is cheap and sold by airlines & travel agents. Having travel medical insurance is a requirement to enter some countries (ex. Lithuania & Slovakia). Even if it's not, PLEASE do not skimp on this as an otherwise-silly accident could turn into a crisis if you don't have medical insurance.
http://travel.state.gov/travel/cis_pa_tw...
Read Christopher Davies's book *Divided by a Common Language*. It gives a lot of information not only on the words and phrases that Brits often use, but also on things that Americans need to know.
You will not piss anyone off, that's a promise. London is a very multicultural city, probably the most multicultural.
There is a large American community here in London - well established over a very long time.
How about spending some time at the house of Ben Franklin?
https://www.youtube.com/watch?v=CPVT-Wje...
https://www.youtube.com/watch?v=-ZcTjOcz...
Don't assume the UK is just like the US - expect culture shock.
Don't talk loudly in public, especially on public transport.
Don't wear back packs in busy places and especially on public transport.
Don't compare the US to the UK, or any other country.
Don't worry. Most of us like Americans. You will feel welcome.
You won't find people striking up conversations in London. They are not unfriendly. They are just in a rush.
Yes don't be too loud and don't wear brightly coloured Bermuda Shorts
You Americans are all the same. No help
Buy a rali pass here in the states It If you are over 60 its even cheaper. When I was there it was called a Britrail pass. .
You are most unlikely to 'piss anyone off'. Have a good time.
