WHAT IF NAPOLEON NEVER INVADES RUSSIA AND DECISIVELY WINS THE NAPOLEONIC WARS?
Well, a relatively unified continental Europe following the same principles of government, systems, currencies, and basic legal code, led at least initially by the French, would form a powerful bloc with a large overseas empire.
Britain continues industrializing with a large overseas empire; Napoleon's Europe does likewise. The United States in the West still has the Louisiana Purchase, but without the collapse of the Spanish Empire won't as easily secure Texas and California without a more serious fight - a fight that the British Empire might be willing to support as a proxy war, hoping to drive a wedge between the member states of continental Europe.
Or in any other non-European region, there would be competition between the British Empire and the Continental Alliance, and that could potentially be a flashpoint for war.
Eventually, industrializing powers are going to invent machine guns, large artillery, poison gas, and trench warfare. And they're going to continue to compete for colonial power, trade advantages, etc. Some kind of war on the magnitude of the Great War is definitely going to happen.
The only way to avoid that outcome is if the Napoleonic Wars are actually concluded by Napoleon successfully invading the British isles and dismantling the United Kingdom, thereby inducting all of Europe into what was previously the continental system. British colonial possessions end up either independent or annexed to a new European master, but otherwise all in the same bloc.
Tens of thousands of Russians never see Paris, bringing back with them dangerous ideas Tsarist absolutism. Early revolutionary events such as the Decembrist revolt do not occur.
Imperial Russia never finds itself as the major European military power, and all the societal and cultural ramifications which came with it. It remains backwards and obscure to the rest of Europe.
Russia continues to appear to be not only the last major bastion of the old order of absolute monarchy in Europe, but an easily conquerable mass of barbarians.
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