In the late 1940s, hearings by the House Committee on Un-American Activities and the use of loyalty oaths illustrate concerns over the
(1) impact of union strikes on the economy
(2) United States participation in the North Atlantic Treaty Organization (NATO)
(3) desegregation of the military
(4) influence of communists within the federal government

(4) influence of communists within the federal government

Explanation:

In the late 40s and early 50s, the United States went through a period known as The Red Scare. It was the second time in history and widespread suspicion gripped the country. There were fears that Communists had infiltrated the US Federal Government. Truman's government also received widespread criticism for being too lax.

In response to this, President Truman signed the "Federal Employee Loyalty Program" that empowered the FBI to check the backgrounds of Federal employees more thoroughly as well as the use of Loyalty Oaths in contracts where the Signee swears that they follow no entity that would want to overthrow the US Government.

Congress also investigated Communist penetration through the House Un-American Activities Committee (HUAC) which took a Frontline position in the apparent fight against Communism.

the united states didn't wanted to get involve with other countries probelms

a.   it resulted in widespread unemployment.