There is a difference between visa
Visa is a document issued by Department of State, in consulate or embassy that allows you to "report" yourself in from of the immigration Officer that will examine you and will / will not let you enter the U.S. If so, he (she) will stamp into your passport a stamp with your manner of entry (i.e. B1 for visitors) and length of authorized stay (in your case it was 3 months) And that is your status
If you are from a country that participate in visa waiver program you do not need a visa to enter the U.S. in visitor status. If you are planning to work or study in U.S. then you will have to have a visa.
Anyway.... any time you are entering the U.S. you have to be inspected by CBP
who will give you new authorization to stay in the U.S. So most probably you will get new 3 or 6 months.
..... guys.. please do not consider myself as a smartass based on above .... please
life is beautiful...