A Third Country Visa refers to a visa application or visa obtained from a US Consulate in a country other than the alien’s home country. Usually the US Consulate is located in Canada or Mexico.
Foreign nationals in the US applying for a nonimmigrant visa at a US consular post in a third country such as Canada or Mexico
Individuals who have ever been out of status in the United States because they overstayed their visa or their I-94 are not eligible to apply at a border post.