Okay, here's what I think about American leaders. Basically, I feel there should be 6 candidates considered.
FDR, Teddy, Washington, Jefferson, Jackson and Lincoln
Now, we don't know how many leaders per Civ. But I feel that Washington will never be left out of the game-- America is one of the biggest markets and Washington's a national hero. Jackson, in my opinion, is probably not well known enough to make it in the game, especially as the more famous national heroes such as the other five are in the race. So we come down to the two Roosevelts, Jefferson, and Lincoln. FDR was one of the most, if not the most powerful President ever. He also accomplished a hell of a lot. Social Security, Medicare, ending the Great Depression, as well as being the head of our nation during WWII. So he should be in second. Ultimately, I feel like TR, Lincoln and Jefferson all represent different interests. Jefferson, as someone else has pointed out, was more expansionist, in terms of city settling in Civ. TR would be the kind of leader who would attack city-states and try to strong-arm other leaders. Lincoln would be the type inclined to avoiding war but be damned good at it if he got into one (firing McClellan, moving Grant to the east). He would also probably put a greater price on defending his territory than conquering someone else's. To sum up:
1. Washington
2. Lincoln
3-5. Jefferson: Expansive
TR: Warlike, but only if he knows he can win
Lincoln: Diplomatic, Defensive
6. Jackson