Please don't mistake unpredictability to untrustworthy, ego-centrism and self gain driven behaviour. The guy clearly lacks any social decency that toddlers even know.
Reagan did this only as a strategy to USSR, but Trump is clearly influenced by self-gain and ego-centric. He is very predictable, if you use that as a variable.
Reagan also supported anti-communism countries and saw the strength in allies. Trump stands alone, every where he goes and doesn't have the brain capacity to lead a country.
I think you haven't been paying attention the last months. The US has never been this divided, Trump resembles a con-man/lunatic a lot more.
Ps. A divided nation is a weak one.