Is it correct to say, “He was sworn in president of USA"? No, it is not. You should rather say “he was sworn in as president of USA."
So the correct way to use ‘sworn in' is that it is followed with ‘as'
1.Barack Obama was sworn in as the 44th president of USA.
2.Amid protests from the opposition, the tainted MP was sworn in as a member of the cabinet.
3. The special officer was given an additional duty and so he was sworn in as the governor of the state.