USA 1350, 04/ 30/ 1789, NY, NY (8/11/13, and ongoing additions)
This BIRTH Chart of the USA, uses the first working moment of the USA as a viable Corporation: CEO (Washington) and as an independent entity, able to secure rights and collect/ print money.
Uranus in the mid-cardinal is a major mover, as It is Now (9/30/15).
From the invasion decimating the Native indians, to the FED (1913: $1.00 then equals less than $0.04 now.), to becoming the most powerful country and longest lasting democracy ever, to the rapidly evolving dualistic society (Wealthy/Powerful vs. the rest), this USA chart signifies it.
The most immediate feature is SA on the Desc trine Jupiter/Moon. These aspects (in partnership with Earth) with abundant natural resources (Sat) and a relatively wealthy populace. Jup/Moon trine Sat gives longevity, along with the sextile to Sun.
Mars/ Transpluto Squaring Moon/Jupiter is a volatile and almost self-destructive aspect, adversely affecting Public Welfare and the Environment. Where's your money coming from and going to? The South didn't like it, and not many nations have survived a Civil War.
Also, if you want a country (as DeTouqueville alluded to in the 1800's) of blind believers (he viewed the US populace as "sheep") then for Astro purposes, given the USA chart has ME Opp NE, what more can you ask. And there is a slightly wider NE Opp Mars/Chiron, = periodic violent and passionate confrontations over beliefs and money. A close description of the motivations behind the Civil War.
9/30/15: The USA creation is the most important dynamic of the last 400 years. The given chart is my current best effort.