Can a US visitor, on tourist b1-b2 visa holder visit Canada or Mexico?

Is it true that if I have been admitted to the U.S. as a non-immigrant, I can automatically be granted entry to Canada or Mexico?

No, entry into Canada or Mexico is subject to each country’s entry requirements.

I am currently in the U.S. on a visitor visa. Can I travel to Canada or Mexico for a short trip?

Foreign visitors in the U.S. will first need to check with the Canadian or Mexican immigration authorities to find out the entry requirements to these countries. Nationals from certain countries are required to apply for visas before entering Canada or Mexico. A valid passport is also required for entry into either Canada or Mexico.

Can I re-enter the U.S. after my short trip to Canada or Mexico?

If you have a multiple entry visa and is still valid, you may apply for admission at the port of entry or pre-flight inspection. If you have a single-entry visa or it has already expired, but your I-94 is still valid, you may still be able to re-enter the U.S. if your trip to Canada or Mexico is less than 30 days. This is called “Automatic Re-validation.”

Can you explain to me how “Automatic Re-validation” works?

Basically automatic re-validation allows foreign nationals with valid I-94s but expired non-immigrant visas to re-enter the U.S. after a trip of less than 30 days to Canada or Mexico. However, foreign nationals cannot benefit from the automatic revalidation process if they have applied for nonimmigrant visas at a US consulate and the application is pending or has been denied. For more information, please check CBP website: http://www.cbp.gov/linkhandler/cgov/travel/id_visa/revalidation.ctt/revalidation.pdf

Who else cannot benefit from “Automatic Revalidation?”

Nationals of certain countries such as Iran, Syria, Sudan, and Cuba are not eligible for automatic revalidation. Visa Waiver Program applicants cannot benefit from Automatic Revalidation, but may be re-admitted for the balance of I-94 under another section of law.