Here is some information to determine what you need in order to enter Hungary.

Where is Hungary?
Hungary is part of Europe's Schengen Area, which is a set of countries within Europe that have no borders between them. Once you enter this area, you have free movement across all the Schengen member countries, as if it were one country. Naturally, these countries share unified entry requirements to enter the Schengen area.
 
To learn more about which countries are part of the Schengen Area, click here (official site of the EU).
 
How do I get into the Schengen Area?
Many non-European countries across the world have agreements with the European Union that waive visa requirements to enter Europe's Schengen Area. If you are a citizen of such a country, then you can enter the Schengen Area without first having to apply for a visa.
 
The USA has such an agreement with the European Union, so US citizens do not need a visa. However, starting in 2024, the European Union requires US citizens to obtain a travel authorization (called ETIAS) before entering the Schengen Area.
 
To learn more how to apply for such a travel authorization, click here (official site of the EU).
 
Important: If you are a US resident, but have another foreign nationality, you may require a visa. Please confirm that your country of citizenship has a visa-waiver agreement with the European Union. If it does not, you will most likely require a visa.
 
For more information on which citizens can apply for ETIAS and which ones need a visa, click here (official site of the EU).
 
For more information on how to obtain a visa to enter Hungary and the Schengen Area, please click here.
 
How do I get into the USA?
US entry requirements work in a similar way. If you are a citizen of a country which has a visa-waiver agreement with the USA, you do not need a visa, but you will have to obtain a travel authorization (called ESTA) before entering the USA. If your country does not have a visa-waiver agreement with the USA, you will most likely need a visa.
 
To learn more how to submit an ESTA visa-waiver application, click here (official site of the US Customs and Border Protection)