Explain why the United States was opposed to the Soviet Union

The U.S was upset towards Russia for their leaders taking Russia out of WW1, and was opposed to a state ideologically based on communism, of course.

Explanation:

The Russian Empire failed to catch up with the Industrial Revolution and this was the main reason it failed in 1917. 
The main cause why Russian Empire did not success at industrialization in the 1800s was the massive land the country was laying on. It was hard for a centralized government to invest in the rural areas, which usually were far away from the main cities: Moscow, St. Petersburg, Ekaterinburg, etc. 
Another important aspect of their failure was that the high classes of the empire showed no interest in investing in industrialization. Starting with the Royal family, to aristocrats, the bourgeoisie and the landlords, there were all cut off from the every day life of a peasant/worker. Even there were exports towards European countries, the profits were usually back to the pockets of the wealthy and greedy. 

The causes: 
Feudal social structure
Csar's lack of interest in industrialization

The effects: 
defeat in Crimean war (the Russian industry was not prepared to face the amount of weapons that were needed)
poor military and railroad system (no industry = no good weapons = bad military; no industry = no good metal & practice = no good railroad system)