The answer to the blank is "limited government." :-)
Answer:
The Machine Gun
Explanation:
There was a significant technological advances during WWI and The machine gun was the most effective during the war. The United States created it and Germans recognized it and was ready to use it.
The fact that mostly everyone in the US was once an immigrant is one. Another is that this is a free nation, we should all be treated fairly.
"Big Business" the government put higher regulations in place during the progressive movement.