The war began as all wars do. An accusation, a spark of misunderstanding, ignites, flaring to life, as long held distrust with all human hearts blazes to life.
This war was no different and as the United States struggled to learn anything about the alien threat that landed in their backyard the world grew restless. Their critics insisted they do more, and demanded more access to the craft. Unable to access the ship themselves America refused, not willing to allowed foreign powers full access.
The world powers did not take this refusal lightly, and united behind the UN they made formal demands for the United States to back down and relinquish control of the alien ship. To punctuate the seriousness of their demand they set ships to the American coastline, weapons trained on the fallen ship, and Washington DC. They gave the United States one week to comply.
America refused the ultimatum, and seven years of bloody war followed.
It was the first war upon American soil in centuries, and its people were not prepared for the carnage of war. Many fled, many more died. United States brought the full extent of it's military to bare to defend it's people. The results were catastrophic and millions died on both sides. The United States were victorious, but the world's military was weakened it's people beaten and afraid. A treaty was proposed, more out of fear, than of a desire for peace. In the end it would be signed, and the nations of the world began the struggle to rebuild. For the first time since before World War II America pulled away from the world, its people began to grow insular, nervous, and fearful.