** spoiler alert ** 
 Really. As much as I hated America's character for not having the time to make up her mind of choosing one of them, here I admit, it is hard to choose even one of them now. 
 Aspen really cares a lot about America and it's clear that he would do anything just for her. Who wouldn't want to be loved like that? 
 Maxon does everything that would make her happy. Hell America probably will be the luckiest in this world to have him. The Crown too, on top of all. 
 it's just because it seemed that America couldn't handle being disliked by the people of the country. And having Maxon's love being shared by 3 other girls in the palace. Besides now that the King himself disliked America which left America with so many reasons to choose Aspen over Maxon. 
 BUT STILL. America won't give up that easily.