Answer is 10%.
About 270 million acres of public land was given away for free to Homesteaders, people seeking to settle out west under the Homestead Act. This constituted about 10% of the US. The first of the acts was passed in 1862, and the second in 1866.
The government system of the Soviet Union during Cold War was communism, which basically abolishes the right of an individual to own a private property. This means that the government has the sole control in all of its resources, thus a greater chance of accumulating and safe-keeping of wealth. Furthermore, during those times war among nations was already at a set off so there was a need to advance their artillery system and other equipment needed to armed themselves in case of attacks. Therefore, most of their resources went to defense spending.
This lead to the understanding among the Soviet Union's people that the current government system was already inefficient and is not viable to sustain the needs of their country. People then demanded a change.
The Native Americans defeated them in the battle of Little Big Horn in 1876
