If he was adopted by Soetoro and went to Indonesian schools he had to have been an Indonesian citizen. He also could not have been an American citizen at that point because Indonesia did not allow dual citizenship at that time. He also, probably, was using an Indonesian passport in 1981 when he took the trip to Pakistan because Americans where not allowed to travel in Pakistan in 1981.
US citizens were allowed to travel to Pakistan at that time. There were warnings of some kind but travel was not forbidden.
Certainly NOT true!!!