as a nation stood united behind
Mostly - but not completely. Check out the editorial sections of the newspapers of the time, where the op-eds and letters to the editor are, particularly in the urban metro areas. All sorts of grousing about sending our boys off to die, what are we doing in Europe and all that. Hardly a nickel's worth of difference between those and our present-day leftists. There's always been a "red" and "blue" America, just without the nasty balkanization we have now.