Anyone coming to the US should have a passport. You might or might not also need a visa, depending upon the nature of your visit.
NO, you need to apply for Transit Visa at the US embassy in Nigeria before you leave Nigeria
flying to usa stop over in transit in heathrow-sa passport do I need a transit visa
No
Yes.
You do not need a transit visa, if you do not go out of the airport to see London or change airports at London.
1) A green card does not mean anything outside the USA. It is your nationality (citizenship) that determines if you need a visa. 2) The UK is not part of the Schengen Area. A Schengen visa is never valid for the UK. You need to ask the UK embassy in the USA (or look on their website) to find out if someone of your nationality requires a transit visa for the UK.
no
Yes you will. Its the US. You need a Visa to enter or pass through the US. Only if you are not coming off the plane.
No, US citizens do not normally need a Schengen visa. They are normally allowed to stay for 90 days as a tourist without a visa.
Visit Beijing for 72hr without visa is now available for transit passengers from 45 countries covering the US, Canada and all members of the EU. Visa-free policy permit transit passengers have visas and plane tickets to a third country to transit through Beijing for a visa-free stay of up to 72hr, aiming to encourage tourism for transit passengers. Sinotour.com.cn offers well-planned Beijing packages with or without hotels for transit passengers as well as business travelers, ranging from layover in Beijing to 3 days packages.
Medical insurance is not required to obtain a US visa however if a visa is granted some programs require that you have medical insurance during your entire stay in the US
Yes, See the US Immigration Page for more details