How were sacco and vanzetti linked to the fear of bolshevism and anarchism?

They were Italian immigrants--following WWI, immigrants in particular from warring countries were seen as dangerous and often target as trying to destroy America. 

Sacco and Vanzetti were Italian immigrants and anarchists accused of a murder in their local neighborhood. Their link to an immigrant group and known union activities led to their arrest and execution. The US entered a time of "normalcy" and wished to rid the US of foreign influence to include anarchists and Communists. 

Iagree ☝️ with that dude

They weaken the south vietnamese army.