What is the protocall for a German citizen to enter the US from Mexico?

Question

A German colleague must come to the United States for one week. Beforehand, he will be in Mexico. Does he need a special visa to enter the United States from Mexico as a European?

Answer 1

No visa needed, just his passport. The passport must be valid for at least six months after his entry into the U.S.

Answer 2

just your passport

Answer 3

No, he doesn't.  Germany is one of the country in the visa waiver program where a tourist/transit visa isn't necessary if your friend spends less than 90 days in the US.