A valid unexpired U.S. entry visa is *not* required if you travel to contiguous territory – Canada or Mexico – for less than 30 days.
If your visa is still valid and it is Multiple Entries, do not need a new visa.
But if it is expired, you need to apply for a new one if back to hte USA from other countries .
let me kno wif need more information:
immigrationtous@hotmail.com