When opinion is molded and shaped by lies...

Here's my uninformed armchair psych anaysis of what's going on. Two things: first, a loooong time since the USA has had a reason, or guidance from leadership, to bond together on a common issue, such as we saw in WW II. This has spawned all sorts of divisive actions and partisanship, like the volunteer military. The second is the loss of trust in leadership, which was always there but strongly increased after Nixon/Watergate, and Reagan's transparent pandering to the wealthy and corporations.

My 2c.