Passport and airline ticket that's it. Before you land British authorities will have you fill out a form asking you how long you will be in the country, where you are going, and why you are there. It is pretty simple to do.
Yes, a US citizen does not need a visa to travel to London for stays up to 6 months.
Yes, US citizens need a visa to travel to London.
Yes, a US citizen needs a visa to travel to Russia.
no
No
money!
Yes, you do not need a passport to travel to the US Virgin Islands if you are a US citizen.
Yes, a US citizen does not need a visa to travel to Germany for stays of up to 90 days for tourism or business purposes.
Yes.
Yes .
yes you do.
yes