Hello! 
I am doing a proofreading at the moment and need help 
with a few issues, as I have been working since 8 o �clock today and my 
mind is not sure of anything anymore.
"Since
1900, United States changed between what historians call "public
actions and private interests."" - I feel the comma is not needed here. What do you think?
"In
another time, they become disillusioned with the social experiments
and focus on themselves." - never heard of such a phrase. I would remove  �at � leaving  �another time � only. What �s your idea?
"At
the
 beginning of the Great Depression, the pendulum swung again, and
Roosevelt �s New Deal and Truman �s Fair Deal focuses on government
actions to alleviate the social misery." - Any ideas about this one? I 
would remove all the commas and changes the word  �focuses � into  �focus �.
"Conservatism
returned during 1950 under Eisenhower, to be followed by a shift in
the direction of liberalism in the �new frontier� of Kennedy
and Johnson �s �Great Society�." - Wouldn �t you add  �s � to 1950 
and have 1950s - this is what I feel with the word during. The New 
Frontier or New Frontier? I would also remove the quoting marks and 
write it in capital letters. The same with Great Society - no capitals. 
"It
reached a climax in the selection of Ronald Regan in 1990." - What about this? It  �reached a climax �
 or it  �reached climax � is enough here?  �Selection � should be  �election �
 obviously, but what about the phrase  �in the election �? Shouldn �t it be
  �after the election �?
Thank you so much for all your answers and help.
All the best,
Finka