Why does it seem that certain atheists' understanding of Christianity is ironically similar to that of Christian fundamentalism?
Most atheists are aware of the different variations of Christianity. They focus on Christian fundamentalism because it is among the most damaging. This focus makes it seem like that's all atheists know of Christianity.
I, for one, will voice my arguments against the belief in God when asked, but see no need to voice it constantly. I don't see most people's belief in God as something that absolutely needs to be corrected, even though I think it is misled. However, for example, teaching creationism in school is just factually wrong, so I do speak out against that whenever possible.
If Jesus Christ came back to life what impact would it have?
I think it depends on where he comes back to life. In the USA, I imagine that he would be met with constant news coverage. If his miracles were continuously caught on film, a world-wide pilgrimage to see him would occur. The US would probably have to limit this influx of people, especially from the largely Christian population of bordering Mexico. The government might even restrict Jesus’ movements for this reason.
If this incredibly documented Jesus could not do miracles on camera because it would no longer require faith from his followers, he probably would not do miracles at all. (Meaning no one would need faith, they would have visual, witnessed proof.) In this case, he would be met with massive skepticism. Jesus would amass some followers, but would eventually lose the public eye. Once he lost the public eye, maybe he could perform miracles and thereby regain the public eye, only to once again not be caught on camera.
Jesus would make a stir either way. Once he eventually died, either by civilian assassination, government intervention or old age (if Jesus can die of old age,) whatever good he achieved would pass in time. New churches would pop up to challenge existing churches’ claim on him. Wars would be fought over where ever the new holy land has become. Atheism, Islam, and Judaism would massively decrease in size; Hindu, Buddhism and other belief systems as well, but not as much. Otherwise, things would go back to normal.
All this is assuming that he doesn't come back Revelations-style.
Which people or organizations stand to gain economically or in other secular ways if the American public becomes more religious?
Whatever company makes those eucharist wafers, cross manufacturers, and Republicans.