Beside this, can I enter us if my visa expires in a month?
You can legally stay in the United States until the expiration of your authorized period of stay. However, you will not be able to travel to the United States Port of Entry to seek a new admission unless your visa has been renewed by the American Embassy in your country of Nationality.
Secondly, what if my visa expires while in the US? When your US visa expires has absolutely nothing to do with how long you can stay in the US. US visas are solely for entry, and the visa's expiration date is simply the last day on which you can use that visa to enter the US. So yes, you can legally stay in the US after your visa expires, if you are in status.
Secondly, how many months before my visa expires can I travel to the US?
Minimum validity of passport at the time of travel is 6 months. Passport expiry less than 6 months is liable to refuse entry in the country and you will be deported. But visa validity required is minimum 3 months, as general minimum stay allowed for long term B2 visa (10 years) is 3 months.
Can I travel within the US with an expired visa?
It is not needed to fly within the US. Fly domestically in US with an expired visa but your I94 is still valid is ok. Visa is only used for your entry into US, once entry is permitted you will be issued a I94 with maximum stay condition stated (in most cases 6 months).
