Why do you need a passport to come from Mexico to California on The bus?

Question

Why do you need a passport to come from Mexico to California on The bus?

Answer 1

if you're a US citizen, you still need proof of it, even if when you talk you speak like a native. Things have gotten real bad w. Homeland Security.

If, of course, you're not a US citizen, you also need an entry visa. Not easy to come by these days...

Answer 2

You do NOT need a passport to travel to and from Mexico by LAND. You need a photo I.D. and a proof of citizenship...EITHER  a passport OR a birth certificate....IF you are an American citizen.  See site below and read carefully.  If you are a Mexican citizen, you need a Mexican passport and a valid tourist visa to the U.S. Starting June 1, 2009, American citizens will need a passport for LAND travel too.

Answer 3

To demonstrate you are not aforeigner trying to get into the USA ilegally.

The matter is for USA safety.