I wonder if you might explain what exactly you mean by this, and to what degree you believe it is a thing.
And to be very, very clear: I'm asking this absolutely sincerely. Not in a clever or trolling manner, but rather, I am asking in an epistemological sense.
I grew up in a couple different Christian traditions, and have known and spoken about this question with people with backgrounds, and/or who currently worship in many others. I have friends and family who follow every denomination from Catholic, to Lutheran, to Evangelical, between, and beyond.
The notions of Hell and damnation not uncommon, though certainly not universal, in the practice of Christianity, particularly among the laity.
Doctrinally, it's less overt, especially among the more liberal traditions, but even there (I'm specifically thinking of Episcopalian and Methodist lineages, here), it's not unheard of.
I think the general theme is going to be ever-present in any Christian religious teachings, but in your experience, do you feel like "heavy emphasis" was put on that particular idea, and especially as a motivating factor for controlling behavior or allegiance....as a tool to manipulate?
And if it isn't confidential, the people you're familiar with, is that restricted to a fairly tight geographical region, or quite spread out? I'm wondering if perhaps it is the case that there are somewhat distinct regional flavors of religious teaching. If this was the case, with a generally more mobile populace, families often tending to live further apart, one would expect this to decrease over time, especially with young people who've moved away from family, although any number of things could cause a change in younger generations.
How overtly employed varies widely, but yes; generally I did and do see it as a tool of control. That the notion is so widespread gives it social proof, so however contrary to doctrine or scripture it might be, it drives our behavior at a far deeper level.
As for your second question, there's a significant subset of my sample population that's moderately geographically bound (Plains and Upper Midwest), but I have people of faith from all over, including internationally, in my social graph, and see some variation on the notion almost across it.
I agree that as people spread out, the phenomenon tends to diminish. Research has shown that a profoundly effective mechanism for combatting insular beliefs is exposure to people who don't share them. Not enough people do that to meaningfully combat the phenomenon, though; something over half of Americans have never left the country, and the median distance adult Americans live from their mother is, IIRC, under 20 miles.
As well, people who move out of places where Hell is more of a thing may lose the belief, some, but many of them are probably leaving because they don't share the belief, to whatever degree, and people who move to those places might already believe it themselves, or may face a group that's selected, positively or negatively (by people leaving) for holding it.
It absolutely was, though. For the Bible, at least, including, in the Bible, Jesus specifically (it's not like we have independent contemporaneous authority besides the Bible on what Jesus said or believed.)
Yet another illustration of the fundamental divergence of that institution from its origins.