Keep in mind that several presidents have served multiple terms, so while there have been 43 presidents, there have been more than 43 actual terms served.
You should also note that although Bush is considered the 43rd POTUS, that figure includes each of Grover Cleveland’s two non-consecutive terms as a separate presidency. Only 42 people have been President of the United States.
He said US, implying “United,” so probably not. Also, the Confederacy was never properly recognized as a nation state, so it’s leaders probably wouldn’t count toward the US total in any case.