If Tadeusz Cosciuszko had not returned to Poland after the war, but rather stayed to establish the states, might he have been the first U.S. President?

President Kosciuszko.
It might have been a reality. Admired by Washington, close friend of Jefferson, and having impressed Franklin greatly, General Cosciuszko might have been elected president if not determined to return to his homeland.
If that happened, would slavery have been abolished during the first administration? Or perhaps would slave owners/traders have revolted, and caused the collapse of the states before they could begin?
What would it have meant for history if Tad had been elected U.S. President?