You should keep your passport valid at all times. Your passport is your own government's permit for you to leave and re-enter your own country.
Most passports contain an expiration date.
Consult your own consulate or embassy in the U.S. to renew your passport. The officials there will tell you what forms and fees, if any, are required. ISSP can provide the addresses of your country's consulate or embassy. The visa stamp put in your passport by the U.S. consul abroad was needed to enter the United States. It does not show how long you can stay here.