FN21.   Canadians do not have to get a visa in advance.  They can apply at the U.S. port of entry, which is actually in Canada at certain Canadian airports, with an employment offer letter, detailed job description, and documentation of the required education and experience.  Mexicans must take the extra step, before they travel, of obtaining a visa from one of the U.S. consulates in Mexico.  8 CFR 214.6(d) (3).