Post World War I Red Scare
This fear of communism and anarchy after World War I resulted in several different infringements on the rights of citizens and immigrants within the US. For example, the Palmer Raids resulted in the federal government organizing a massive raid and arrest of thousands of people. This was out of fear that these people were organizing a violent attack and overthrow of the American government. These homes were often searched without warrants.
Post World War II Red Scare.
This was similar to the first red scare in the sense that citizens had their constitutional rights violated. An example of this would be people being accused of crimes (such as being communist) without evidence or proof. However, the Second Red Scare differed in that it unfolded on national television during the McCarthy trials which took place in the US Congress.