I think Lelouch would make a great president and would be able to unite humanity if given the time.
I could see C.C. as Secretary of State, or mostly any role in office. Other examplse: Secretary of Defense could be Tohdoh, Secretary of Energy could be Rakshata, and Secretary of Education could be Ohgi.
Lelouch would likely call for a new constitution for America (the world has changed since 1787...), rid corruption from goverment, make better relations with people around the world, form a effective assassination squad for our enemies, better education for our children, real equality for all race, gender, and religion (except if the religion is one of violence or hate), get rid of the broken two party system, put corporation in their place, advance technology and create a new energy resource, and eliminate any threat to the people by any means.