You know, so many new traits are suggested for America, but part of me thinks the most interesting and fun way to go about it would be to simply add on the ability to purchase tiles owned by others. It would turn them into a civ that establishes a sort of inherent territorial domination, and by very merit of playing them you'd take advantage of that trait and forward-settle the hell into peoples faces and buying up choice land with the power of CAPITALISM! And you can go ahead and buy natural wonders owned by others, or tile improvements, or just troll them and completely strangle off a city until its only tile left is the actual city.
...Really, "peaceful expansion" hardly defines America. The very term "Manifest Destiny" entailed a sovereign right to push into land and the assimilation of other cultures into the ideals of America. Expansion above all else, even if someone else owned the place. Of course, doing this in-game would be akin to a Citadel bomb diplo hit for each tile, and if you settle like this, you must prepare to back up that claim. And playing against America, you probably will have to take the plunge and actively defend yourself from their approach.
Really, the biggest thing vanilla civs need are active effects. Simple passive effects are what made them boring in the first place, but interesting yet easy to grasp unique gameplay mechanics are what gives the best flavor and makes playing that nation really feel like you're, well, playing that nation, and not just a generic civ with slight touches like that country. Extra yields from bonus resources are nice and powerful, but also just sorta boring. There's only a couple occasions where they'll really typically give anything more than 3 or 4 food and/or production, and settling a new city will still largely be determined by the presence of luxury resources in the area. And it's never going to amount to a unique game in the end. Civs are more interesting when you're given moments to dramatically sweep your cape to the side and launch your UNIQUE SUPER ABILITY, SUCK IT on someone else. Something satisfying to actually do, giving you a "hell yeah, cause I'm America all up in here" moment. And gleefully buying someone else's tiles definitely qualifies as that. But then, that of course needs to be countered by any given opponent having their own UNIQUE SUPER ABILITY, SUCK IT to send to someone else. Yeah, go ahead, forward settle on Assyria, you better have the force needed to back it up, because they'll Siege Tower your ass. As the Polycast put it so well, "screw your neighbor" techniques are always fun, and that's kind of a thing early-game BNW is lacking at the moment, interaction of screwing with each other and making power plays to take the advantage. There needs to be dynamic unique aspects to a civ that you can base a strategy around. What do additional food and maybe a few more points of production entail for the unique way you'd play America? Slightly bigger cities? So? The Aztecs can do that several times better by just building one UB, and they get sacrificial super-culture and the best early infantry unit in the game. That's not going to make America any more fun to play. It will make them more powerful, but power isn't the matter here. It's intrigue. Something that you'll be excited to take advantage of, and satisfied when you do. That's what makes a good civ.
instead of +1 
instead of +1 
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