Curious, how much of the current state of the Republican party can be blamed on Reagan? If I recall correctly, he did have a heavier focus on religion, American exceptionalism, and the military than prior Republicans...
Wanted to answer this, but I've been gone all day.
Reagan captured lighting in a bottle, there's no doubt about that. He took a good situation and used his PR and acting skills to make it a great situation (in this way, he is Trump's ironic mirror). I hate Reagan, but he was competent and after a fashion rather moderate in a way that captured most of America. It pulled the country as a whole rightward since the party is much more than the President's agenda, but Reagan instituted several policies I'm sure you've heard about for how they would get a modern Republican crucified.
The trifecta of social conservatives, economic conservatives, and hawks existed before Reagan but they had much, much lower crossover. The 70s have firmly passed into "real history" now, and this is why there's all sorts of weird incongruities like far-right churches arguing for welfare (for white Christians, at any rate) and what remained of the pre-realignment Republicans' social liberalism (see Barry Goldwater, right-wing eternal champion's candor against society for mistreating gay people). And the hawks definitely had a problem in the form of literally everything about Vietnam and there being a lot of people who remembered McCarthyism for the man himself. In a way, all this lack of unity turned into a strength when Carter started to lose popularity, because they were willing to give away secondary issues in exchange for the same from the other groups, and it was Reagan who sat at the center of it.
As for the Republicans today, their biggest thing I think is trying to make that lightning strike twice. The coalition is still solid (mostly, RIP religious right, only Pence is your savior now) but the membership is facing some endemic problems. Reagan is often satirically referred to in religious terminology for a reason, the eternal issue of nobody knowing what they're actually doing means the GOP's positions are often a legacy of the things Reagan did that they liked most, because surely if they just do what he did it will work out the same way.
Of course, if Reagan were around to see Trump, it would probably be at best with the eye-twitch of can't-say-anything-but-what-the-ever-loving-fuck.