Farming leads to feudalism
Reading, writing lead to the codification of religions for the millennia
Printing - allowed the breakdown of the Catholic Church, the Protestants. The protestors. The Great Awakenings where anyone can publish a holy book about a new religion cheaply and efficiently.
Mass printing allows the invention of the Newspaper - mass delivery of information, does this information have to be true? Nope, no way, not even most of the time. The owners of the newspapers print what sells: Yellow journalism was invented before nation states.
Power if you need it.
Individual message delivery.
I can telegraph almost anyone in the world. Great ocean spanning cables are laid, laying waste to many species of insects, trees and animals used to manufacture them. My empire can be world-wide and I don't have to wait months for information to travel at the same rates as goods on ships. I can get the info in a few minutes.
This allows nation states to really come into their own, spanning continents, creating the final form of colonialism, where Europe enslaves the world to produce goods for Europeans at the expense of native populations.
Photography. At this point in time photographs don't lie. The terrible consequences of slavery and colonialism become obvious to the average person. The shift in minds is irreversible. Abolition gains world wide acceptance. Feudalism ends across Europe.
In the US, desperate to save their economy, the Slave states revolt but are crushed in a brutal civil war.
Andrew Johnson gains the reigns after Lincoln's death and tries to absolve responsibility to protect the rights of ex-slaves, he's impeached but not convicted by one (bribed) vote.
Reconstruction end soon after and Slave states begin passing black codes that allow them to arrest and force blacks into slave labor. The federal government claims it has no responsibility to protect the rights of all humans (Dred-Scott decisions.)
The telephone comes of age! I can now call anyone anywhere, soon to be available world wide. The telegraph cables are converted to telephone, soon to be converted back to data. Empires can now get instantaneous information from any part of their empire. Wooden ships are replace by iron ships. The countries that can't keep up soon lose their empires to the new upstarts that figure out how to build ships their enemies can't sink.
Jim Crow comes into its own. It's apparently illegal to be black in the south and use any public facility. It takes many decades before the US Supreme Court finally rules this illegal and unconstitutional.
Electricity and associated systems are invented by Edison at General Electric (GE) and Tesla at Westinghouse and spread around the world quickly. This power is much more portable (as compared to steam) and begins a quick end to farming as the main employer. Farms no longer need thousands of workers.
Mass death machines (machine guns and tanks) are built. Chemistry creates cheap explosives (dynamite) and the kill ratios per dollar continue to rise exponentially, peaking almost 100 years later with the invention of the Hydrogen bomb and ballistic delivery system which can produce hell on earth in an instant. Humankind thinks it's a good idea to produce enough bombs to turn every square inch of the earth into hell many times over. They still do.
1900 to 1920
Radio is invented. The first real mass communication media (you don't have to read, literacy rates are still preventing the newspaper's ideology from taking over the minds of everyone.) But now the leader can speak to everyone at once. This leads to the politics of simpletons (royalty is slowly replaced by the cult of personality) in many countries, i.e.; fascism and communism are new governmental theories where governments and the capitalistic companies gang up together to control the means of production. In the US we opt for a more cooperative form of socialism (FDR) which saves our country from another revolutionary war.
1920 to 1940
Film is invented. People can see entire histories. Film makers make what sells. Imaginary histories fomenting genocide (Gone with the Wind, Nuremburg Rallies, The Birth of a Nation) are widespread and popular. This does not calm humans down, in what was thought to be the last gasp of war, we kill tens of millions of people. Then we do it again twenty years later, but this time we kill hundreds of millions. Hundreds of thousands die in a single day in the dreaded fire storm bombings in Germany and Japan. This is still hard work. It takes mass armies and air forces to deliver mass death.\
1940 to 1980
Science builds the nuclear bomb and the ballistic missile to deliver it. At this point we can destroy any city on earth in one hour. Mutual Assured Destruction becomes the accepted mythos of a Superpower. Wars start to become smaller and more limited. Deaths from starvation, deaths from war and deaths from genocide continue to dwindle.
In the US Jim Crow laws are declared unconstitutional. The Civil Rights Act and Voting rights act are passed in the US. This causes the confederate states to continue racism under whatever guise they can: from no blacks voting for over one hundred years to a higher percentage of blacks than whites voting. Whites still hold the vast majority of power. Public works are destroyed because they would have to be shared with the lower caste. There's a big push to privatize government so discrimination will be allowable. School integration begins by firing all of the black teachers and shutting down black schools.
1980 to 2010
Mass delivery and world wide supply chains become common place. America exports its efficiency to the world and continues its globalization policies. Any person in the world now has access to more information than any King ever. They also have more access to disinformation than ever. Lies can now spread at the speed of light. Truth is still limited to the scientific method and its antiquated peer review and publish or perish ethos. Science doesn't care who you are, it's all in the reproducibility. Even though scientists are humans and prejudiced, the system is not racist. Nobody knows you're a dog on the internet.
The Internet explodes from three nodes in 1969 to billions*. Misinformation and propaganda are available at a click of a button, carefully curated by artificial intelligence to increase the time humans spend looking at it, dragging vast hordes of idiots into further radicalization. What was thought to be the most efficient mode of production and delivery in the world (the sears roebuck catalog and the US postal service) are now woefully inefficient by comparison. Next day delivery of anything anywhere is now possible with one click. Real information is also available with one click as search engines leverage all the hyperlinks to determine what is popular; electronic delivery of books (where the real wisdom is held) becomes instantaneous. The limiting factor is the attention span of humans.
2010 to 2020
Localized, stylized, personalized communications point to point. Targeted marketing is perfected. Everyone has a platform to broadcast to everyone. Social media companies don't care how they get their audiences, they don't care if it starts to tear society apart or not. They have learned how to monetize outrage and it feels good! Individual messages can be targeted to individuals that radicalize and increase their usage which leads to immense network effects magnified beyond belief. Mass shootings become common in countries with guns. Pogroms, which had been diminishing start to creep up again. Genocide is now pushed down to the individual level. And it's only going to get worse.
2020 to 2030
The social networks become personalized communicators that lure you into friendship, not only do they curate your feed, they create your posts. They know what you want more than you do. They control you to maximize the profits of corporations. Amoral corporations. Governments will be overthrown. Death and mayhem will return at unprecedented levels. Control of populations will extend far beyond persuasion as people see they will be left behind in the lower caste if they don't get the latest brain implants and genetic modifications to extend their lifetimes. The human race will enslave itself to survive. The death march to competence and expertise will drown our humanity. Unless something changes this is not going to end well.