Why do the think the united states and western europe countries were concerned about soviet expansion?

Western Countries were concerned with Soviet expansionism as a threat to western ideals itself; Capitalism and Communism represented two vastly different ideals in how to manage everything in life that a 'conflict of civilizations' mentality applied; Everywhere communism went was bad in the eyes of the West, and everywhere capitalism went was bad in the eyes of the East.

It allowed for things to be produced much more quickly and efficiently