So who would actually win if it came to an all out war between Russia, the USA and France Entente vs Allies Germany, UK, Italy, Japan and AH in this time period?
Where would the non-Great Powers fall, Ottomans?
Could the USA keep France and Russia in it? If France and Russia go down I don't see how the USA can stand against the world in 1900. Isn't there a thread about the point when the USA can survive to eventually beat everyone?
There tends to be, as these threads always go from "Can X beat the US in an invasion" to "Can X+Y beat the US in an invasion" and etc until it becomes can everyone combined invade the US, regardless of the how or why, and it must be because the US has too much badboy like this is a Paradox game
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My bigger question is to why the US is in a world war against the British and Germans and AH and Italians and Japanese in 1900 - it's one thing, feasibly, to discuss the Germans going out of their way to try and cut the US down to size when they are busy in a war in the Philippines trying to control the islands. But why is the US fighting all at that point in time when there's no reason for the US to join in such a war? And, if it's a Coalition that has assembled, then how did it assemble?
Regardless, the ability to threaten the US is predicated on whether can secure enemy (read: British) territory in North America before France and Russia fall. If they succeed, they will be able to deny the enemy bases in North America, meaning they will have to fight at the end of their supply lines, with all of the disadvantages that such combat would entail. If they don't succeed in taking all of the local bases, the Anti-American Alliance of Convenience (AAAC) would have their base of operations and could operate locally without as many issues.
Still, there's no way to answer your question as there's no background to determine how this alliance forms and why the US decides to fight all of these other nations simultaneously, or why the UK & Germany would rather ally with each other to fight the US, or why the US cares enough about France and Russia to align with them in such a war.