Is it visa-free to go to Britain with an American green card?

You can't go to England without a visa. You need to apply.

Can I get a visa-free country with an American green card?

Landing visa is still visa-free

Central and North America:

Canada (6 months), Mexico (6 months),

Antigua and Barbuda, Aruba (14 days), Bahamas (30 days), Cayman Islands (30 days), Costa Rica (90 days), Dominican Republic (30 days), San Salvador, Jamaica (6

Month), Netherlands Antilles (14 days), Turks and Caicos Islands (30 days)

Conditional transit visa-free (you can leave the local customs)

Japan (72 hours) South Korea (30 days), holding visas from Japan, the United States, Canada, Australia, New Zealand, the European Union and Switzerland, staying permanently, and going to or returning to these countries through South Korea. Singapore (96 hours), Japan, the United States, Canada, Australia, New Zealand visas, permanent residence (valid for more than one month).

Brunei (72 hours): Airline guarantee is required.

Britain (24 hours), holding visas from the United States, Canada, Australia and New Zealand, leaving these countries for destinations, or going to these countries from other countries. Holders of American green cards or Canadian maple leaf cards also enjoy this treatment. However, the holder of the US temporary green card stamp I55 1 on his passport cannot enjoy this treatment.

Hong Kong and Macau (7 days).