Do you need a passport or aa visa to visit the Uk from America?

Question

Do you need a passport or aa visa to visit the Uk from America?

Answer 1

you need a passport anytime you leave the country

you only need a visa if you are going to live there for a long time

Answer 2

you need a passport

you can visit the Uk for up to 6 months from the U.S without a Visa

if your visit is going to be any longer than 6 months, then you need to get a Visa