Yes.  Permanent residents and/or citizens can sponsor friends and family in Vietnam to come over to America.  Please note that visitor visas are for a short duration.  To obtain a visitor visa:

- a relationship must be establish between the person in Vietnam and America

- there must be enough financial proof that expenses of a visit can be provided for (this can either come from the Vietnam or American side)

- proof that there are reasons for the visitor to go back to Vietnam

Please also note that there are many different types of visas, it is best to consult an attorney for the best type of visa available for a “visitor”.