France not selling the Louisiana Purchase would have massive affects on history, for sure. The most immediate changes are discussed in an essay from the What If? Book called "Napoleon's Invasion of North America". In that book, it suggests that Napoleon would have fled to America after being defeated in France, until he is eventually defeated at the Battle of New Orleans.

This means that Louisiana's fate, and by extension the rest of western North America, is decided by the European powers in the Congress of Vienna of 1816. Colonialism of America is still the norm since the Monroe doctrine won't exist for nine years, and the fledgling United States had only just recently made peace with Europe in the Treaty of Ghent.

The Congress of Vienna could decide to return Louisiana to Spain (who Napoleon stole it from), give it to Britain (and merge it with Canada) or keep it with France under the restored Bourbon dynasty.

Had they given it to either Britain or Spain, then the USA's influence in the world as a superpower would be severely neutralized. Much of America's population, resources, and manpower would be greatly limited, and America's influence over the western hemisphere and the rest of the world in the 20th century would be a lot smaller, if it exists at all.

The Texas Revolution is butterflied away because American plantation settlers can't reach the Mexican Empire, and California would likely still be part of Mexico, if not an independent country. Hawaii would likely become a European protectorate, possibly Britain or Japan, until its eventual independence in the 20th century as a monarchy. Alaska would likely be sold to British Canada. On the flipside, the US Civil War is butterflied away too, because there are no western territories to dispute over. The US would likely abolish slavery later in the century under peaceful terms.

If Louisiana is given to Spain, then it would likely become an independent country almost immediately. The Spanish Empire was quickly collapsing in the 1810s into the 1820s, with their entire colonial sphere breaking off as independent. An independent, powerful Louisiana is something I've seen in other timelines on the Wiki, but certainly not explored nearly enough in my opinion.

If Louisiana is given to Britain, then that would make British domination of the western hemisphere more secure. The Monroe doctrine wouldn't exist, as Britain would assume responsibility to police the Americas and systematically end colonialism. With Britain's support, then the Second Mexican Empire would likely not fall, and Spain would control the Dominican Republic a lot longer.

After World War II, either scenario faces a significant problem with the rise of communism under the Soviet Union, since there is no superpower to match the Soviets. All the US-backed coups and proxy conflicts around the world are either done with a lot of help, or never happen at all (Korea, Vietnam, Israel, Iraq, Colombia, Bolivia, Afghanistan, Iran, Taiwan, etc.). While the US might still develop the Atom bomb and NATO with significant help from the rest of the West, I could see the USSR being a lot more successful before their eventual collapse.

There are kind of two basic approaches. One is for when you really want to explore the consequences of your point of divergence. For something like that, you really have to move kind of slowly, almost year by year, looking at how the situation plays out and adjusting things accordingly. This is sometimes called "hard AH" or "counterfactual history" and is considered the most realistic way to write it. It takes a lot of patience, and you won't really know how things are in the present until your story gets there on its own.

The other approach is to start with the end in mind, have a basic plan for what you want the world to look like and sort of write the events around that plan. If you want the world to look really different, decide now how different you want it to be, and make a basic outline or map about it. This is considered less "hard" and realistic but is still a valid way to write AH.

Either way, as you write in more detail you might find some surprises that take history in different directions from OTL. For example if you stay committed to the list of nations that you made, when you're working out their relationships you might find that your version of a world war has totally different sides and motives. Or maybe they find a way to avoid the great war entirely and it plays out as a series of smaller conflicts. But no matter what, the answer will involve exploring your setting in more depth.

Re: Nathan1123

Hi! Thank you for responding, I really appreciate it. My original idea for an independent Louisiana was to have it be granted independence to act as a buffer between the UK and US after the War of 1812 however I think the idea of granting it to the Spanish is far more realistic and will most likely be the route I choose going forward.

However, I originally thought that without Louisiana Southern need for expansion might increase instead of being blown away entirely without westward territory as now the north has a far stronger majority to just outright outlaw it. With this more intense need for expansion I thought that more states may secede and even grant the CSA it's independence. And with the CSA in there WWI and WWII would probably be much different.

I guess I'm not really one for super hard Alt Hist and just more so "this MIGHT have happened if X happened, so what if it did". Makes things a lot more interesting I guess. Though your point of no outright opposing superpower will actually help a lot with the Cold War Era history I've been struggling with for awhile, so thanks for that :) I just thought that there might've been a way to change just the basic strokes of history but I have a feeling they're unavoidable by the 19th Century. TYSM again!

Re: Benkarnell

Hi thank you! I'm aware of the difference between hard and soft and sort of lean between the two (sometimes I go with a consequence of a change in the TL other times I work to figure out how to get a certain result though I generally try to stick to what's mostly realistic) but I thank you for giving me a little more in depth of a response regarding the two so I can use them for further reference :)

That list of nations I have so far is completely tentative though as there are some parts I still need to work out and others that I'm very intent on holding onto. My main goal is to just make a TL that is somewhat plausible but at the same time changes as much as possible about history as a whole both in government, history, and borders :) TYSM!

OK, cool. I'll add though that nothing is ever inevitable, and that if you want a world where by 1950 there are no superpowers, or there's only one, or there are three... all are absolutely possible given a change all the way back in 1803.

In my Alternate history France wins the seven years war, so liberalization is still going on to this day, as well colonial empires still exist in Africa and Asia, and lots of Europe remains with Monarchies, WW1 would still happen around the same time it did because of colonization, but the Germans are not united so Germany and Italy as well, along with the balkans would be the battle ground in europe, not france and Russia

Thats just one way to make a good PoD, but you can also make stuff that wouldn't happen, well happen in your timeline to alter the political landscape of the world.