Are you talking about Pete Seeger or someone else?
On August 31, 1935, Congress passed<span> the first </span>Neutrality Act<span> prohibiting the export of “arms, ammunition, and implements of war” from the United States to foreign nations at war and requiring arms manufacturers in the United States to apply for an export license.</span>
The correct answer is - pull factors.
The increased freedom and much more employment opportunities in the United States can be considered as pull factors. They can be considered as pull factors because they are big reasons why people from all around the world got attracted to the idea of migrating to the United States, as they saw a nice chance to prosper and have a better life. Most of the countries were still struggling with the freedom issues, and the employment opportunities were either very limited, or badly payed, so no wonder that pople wanted to move in the United States.