Answer:
1. they finally joined the war because Germany embarked on a deadly gamble. Germany sank many American marchent ships around the British isles which prompted the American entry into the war
First Answer:
The socialism never found support among the people in United States due to small power of the workers Union. Also, companies have more political and financial power over their demands.
Second answer:
There could be more support for the homeless and poor people in big cities. Health care and some childhood protection against poverty might be another benefits from it.
Third answer:
The negative aspects we could imagine as the political power of unions increased among the workers. They would start attempting a coup across the country in order to start a social-communist regime. Another problem could be the increase in corruption, based on the good faith of the poor, that is, they could "buy votes" among the poor by threatening them with benefits' cut if the worker does not support them or does not vote for them.
Different races can now go to the same schools
It got larger and more states and colonies were discovered
It is useful so that way people understand what happened years ago.