Warlords. Mass panic. Massive amounts of debauchery and betrayal. Violence like not many are experienced with dealing with. Expect things you had not thought of, mostly negative. Expect few heroes, and many villains to one extent or the other.
  How far out, time-wise?
  Well, the oil is going to run out. Don't ever forget that. Once it does, no more airplane travel, automobile travel, or power grid. Electric cars depend on power from petroleum products. The manufacturing of solar panels depends on it too. Solar panels are also made from things that are in limited supply, and have to be transported. All of this is covered WAY more expensively by others (like John Michael Greer) elsewhere, so I'll not go on.
 Cash will lose it's value. This is happening now. For a while, metals like silver and gold will retain or increase in value, but as the technological world deteriorates, even metals will lose value. You cannot eat, drink, wear, or breath silver. What will be of value in the material world at that point? Food. Shelter. Water. Fire. Sex, perhaps. Same as 100,000 years ago.
 The Earth will not return to how it was 100,000 years ago though, because humans have polluted it heavily. There was no plastic in the fish, in the breast milk of humans, in the blood, in the water, a thousand centuries ago. There is now.
 Expect leaking radiation. Expect it to increase as time goes on. No one will have the ability to regularly recontain all the radioactive waste now contained. It will leak out. It will deform. It will sicken. It will kill.
 Humans may not die out from this though, because they may have already died out. The testosterone levels are dropping. The plastics are feminizing males. One reason, though not the only one, that we see more males attempting to be or act like females, is because there testosterone is so low, they feel more feminine than masculine. We really are not, physically, producing the men we used to produce. This trajectory will continue and may lead to extinction of our species.
 What of America? Short term, a temper tantrum, as it loses it's dominance, prestige, and influence. Probably a continuation towards and then full on dictatorship. Eventually, the breakdown of the country into smaller factions and states. Soldiers on horseback.
The warlords and soldiers will have advantages over the general population. Many of them will smear synthetic testosterone over their arms, legs, and balls. They will therefore be stronger, more assertive, more able to solve problems, etc. Low testosterone of the masses will make them easier to dominate and control.
 The population will decline, steadily or in great hops. 
 All the people into freezing their brain, all the crypto-believers, all the transhumanists, all of them will fail in their goals. The transhumanists bodies will rot or be eaten, their brains included. Their thoughts will not live on in cyber space. There will be no cyber space. The whole internet, "cloud", "AI" (there is no such thing as artificial intelligence, it is simply a language model---unalive) will end for good. No power, no computers.
 Is there any hope? Hope of what? Materially, no. Spiritually, yes. Nothing can stop you from saving your soul. Nothing can stop you from loving others. The world was always destined to end, and end it will.