How did the Soviet Union actions affect the US?

The soviets responded with its own military buildup, beginning an arms race that would go on for four decades.

Why was the Soviet Union a threat to the United States?
Because USSR was a mass mobilizing totalitarian dictatorship, which occupied most of Eastern Europe, killed and arrested political opposition and even ethnicities seen as a threat to Kremlin, and ran large and influental communist groups/parties in all the western democracies with an ultimate intent to influence…

The Birth of a Nation (originally called The Clansman) is a 1915 American silent epic drama film directed and co-produced by D. W. Griffith and starring Lillian Gish. The screenplay is adapted from the novel and play The Clansman, both by Thomas Dixon Jr. Griffith co-wrote the screenplay (with Frank E. Woods), and co-produced the film (with Harry Aitken). It was released on February 8, 1915.

Three hours long,[5] the film was originally presented in two parts separated by an intermission; it was the first 12-reel film in America. The film chronicles the relationship of two families in the American Civil War and Reconstruction era over the course of several years: the pro-Union Northern Stonemans and the pro-Confederacy Southern Camerons. The assassination of President Abraham Lincoln by John Wilkes Booth is dramatized.

The film was a commercial success, though it was highly controversial for its portrayal of black men (some played by white actors in blackface) as unintelligent and sexually aggressive towards white women, and the portrayal of the Ku Klux Klan (KKK) (whose original founding is dramatized) as a heroic force.[6][7] There were widespread African-American protests against The Birth of a Nation, such as in Boston, while thousands of white Bostonians flocked to see the film.[8] The NAACP spearheaded an unsuccessful campaign to ban the film.[8] Griffith's indignation at efforts to censor or ban the film motivated him to produce Intolerance the following year.[9]

The film's release is also credited as being one of the events that inspired the formation of the "second era" Ku Klux Klan at Stone Mountain, Georgia, in the same year. The Birth of a Nation, along with the trial and lynching of Leo Frank for the 1913 murder of Mary Phagan in Atlanta, was used as a recruiting tool for the KKK.[10] Under President Woodrow Wilson, it was the first American motion picture to be screened at the White House.[11]

Griffith's innovative techniques and storytelling power have made The Birth of a Nation one of the landmarks of film history.[12][13] In 1992, the United States Library of Congress deemed the film "culturally, historically, or aesthetically significant" and selected it for preservation in the National Film Registry.