Winfield Scott maybe? Man, that could be so awesome, even if made into a cracky/fun timeline, that could be so awesome.
Winfield Scott was a great general. But his personality was so off-putting that he'd fail to gain the political support to become an American Napoleon.
On the other hand, while he was in command of occupation forces in Mexico City, a group of Mexican elites approached Scott and invited him to become President of Mexico. He declined. But if he had accepted, he might have become a sort of Mexican Napoleon.