What did most americans understand before their country entered world war i?
o that the war would not last long
o that the war would cost american lives
o that the war would thenh/s economy
o that the war could be won by the us alone

most American understood That the war would cost American lives  ( B )

Explanation:

Most Americans understood that joining the world war 1 by sending their soldiers to fight would cost the lives of their soldiers ( American live ) because most American soldiers as at the time of world war 1 were not properly trained and used to using the modern war equipment being used by the Europeans. Nobody knew how long the war would last so most Americans did not understand that as well. the war could not be won by the US alone that was understood by all including the Germans and the British even Americans at large. they didn't understand how the war would help their economy either.

to oppose fdr’s new deal

explanation:

the american liberty league. the american liberty league was a nonpartisan organization formed in 1934 in opposition to the new deal. the organization's stated goal was “to defend the constitution and defend the rights and liberties guaranteed by that constitution.”