Here's how I see it:
Dr. Killian heads up a mega tech firm called Advanced Idea Mechanics. He's just signed a major defense contract with the US Army to supply battlesuits based on the War Machine design (maybe Rhodey is retired, and has gone to work for AIM as a consultant? Just spitballin' here). Unveils the Iron Patriot armor in honor of Captain America. Maybe the Firepower armor, too. US Army is putting together a brigade of armors.
Meanwhile, other countries are putting together armors, too. At least China, for sure. Maybe AIM supplies them, too. In any event, you've got a new arms race going on, but instead of nuclear missiles, it involves cheap Iron Man suit knockoffs, courtesy largely of AIM and the nifty new Extremis nanotech.
Meanwhile, in the shadows, AIM is secretly being funded by international terrorist group the Ten Rings. Their leader, Mandarin, plots to engineer a full-scale war between the US and China, because this is essentially World War III, the last two superpowers duking it out to be Last Country Standing.
How does he do this? By having the US President assassinated. While the Pres is visiting Miami, Air Force One is attacked by what appears to be Chinese armors. But it isn't really; just a false flag attack engineered by Mandarin. So as the US and China stand at the brink of war, Tony Stark uncovers the Mandarin and his plot, and realizes it's all a ruse. The only problem is that nobody will listen to or believe Stark....so now it's up to him to literally save the world from nuclear war....
