@kobuk its because usually democrats/liberals (hillary's side) are pushing for alot more foreign aid and money leaving our country while republican/conservatives (trump's side) are pushing more for money/jobs staying in america.
in other words republicans are the ones saying we need to take care of our selves first while the democrats are saying we need to help everyone.
while the republicans method of doing things and what they sometimes say is disturbing/undesirable they do seem like what you are talking about which is we are all Americans, and they are pushing for us to be unified. hell my viewpoints and opinions point towards far left liberal but iv been siding with the republicans lately since i agree with what they say which is he need to take care of our selves first, and unification while the democrats/liberals are doing the whole "us vs them" thing with labeling them selves as black, lgbt, etc. the whole race issues were kinda gone awhile ago yet the left still bring them up and whatever.
some labels are useful but only if you can manage them correctly. so far the left is doing horrible at that.