Answer :
One way in which the US job market changed after World War II was that "US companies grew during the war, resulting in more professional, white-collar jobs" since the war demanded so much output.
I believe the answer is: US companies grew during the war, resulting in more professional, white-collar jobs.
the expense that occur during the war must be paid by the losing side (italy, Germany, and Japan) , plus additional interest. Since the allies won the war, United States and other allies in western European countries experience an economic growth, which resulted in development of many white collar jobs.