What documents do I need to enter the United States?

To enter the United States, you will need several documents. Firstly, a valid passport is a must for all foreign visitors, except for citizens of the countries participating in the Visa Waiver Program (VWP). If you are a VWP citizen, you will need to possess an approved Electronic System for Travel Authorization (ESTA) prior to travel. For non-VWP citizens, a visa is usually required; the type depends on the purpose of your visit. Additionally, you should carry any supporting documentation such as a letter of invitation, proof of accommodation, and proof of financial means. If you are a lawful permanent resident, a US Permanent Resident Card (Green Card) is necessary. For US citizens, a valid passport suffices, but it's highly recommended to also have a Trusted Traveler Program card like a Global Entry card. Always check the specific requirements well in advance to guarantee a smooth entry into the United States.