So in this timeline America, for one reason or another, pursued stronger relations with Germany rather than Britain, and by the time WW1 happens, they had a similar standing with Germany as America did with Britain in otl. America doesn't join at first, instead doing for Germany what they did for Britain in otl, but eventually they do join, likely for similar reasons as the real world. What is the most likely outcome of this?
As others have said, it would need a longer lead time to be realistic. That said, if we handwave the situation to be OTL like in 1914 with the start of the war, or even the murder of Franz Ferdinand. Then we could make some observations:
- The Entente would have to massively overhaul their industry to face the new situation, as in OTL the relied on the USA for massive amounts of raw resources and semi finished products. So that will have a massive influence right from the start.
- Next is the whole monetary and supplier situation that chages. Without the USA as a willing trader who is able to supply the Entente and what is the difference in effort to get the amounts to Europe.
- Another point is that this USA probably would be very unwilling to defere to the Entente in questions of blockading policy. So a distant blockade would be more dicy and the whole slew of questionable Entente choices, ie freezing neutral trade and checks in Entente ports, will further worsen the ATL situation.
- Further you have a different balance of neutral oppinion to work with. So if the USA is more CP leaning how is Canada reacting. Or Italy if they "know" the USA is different.
From this I think the changes would be accumulating from the start. Would it change the 1914 situation? Maybe not that much to matter but from 1915 on the changes will matter. As the Entente would be forced to fight another kind of war. Not the "rich mans war" they did in OTL but one were they have much less margine for error. On the other hand, the CP will have some more room to work with here.
After 1914, I think the first mayor point that could change is Italy. Maybe they enter as OTL or maybe not. Depends on the situation domestic and diplomatic. But my feel is they will enter as in OTL. Maybe more promises by the Entente will be needed but I think the USA is far enough away to not matter yet.
That lets us determine that 1915 probably still largely follows the curse of OTL but there will be some differences. The Entente will have to economize much more from the start. At the same time the CP may be able to spend a little more in supplies. And that probably will show in a better casualty rate for the CP vs. the Entente.
The point were it opens up for me is then 1916. Here the pressure on the Entente supply because of longer distance LoC and U-Boot threat should impact the war noticably. And I think the CP will know that they have the upper hand. They are probably doing as good in Russia as in OTL and "better" in the West, less losses and better supplies will see a better situation for them. At the same time I could see the clock ticking for the Entente as they have to juggle more mayor balls then OTL.
In the end here, I think if the USA then enters or not is a matter of flavor for a TL. Because Imo without the USA supplieing the Entente with money and materials as well as opening the trade to Europe above the levels of OTL the CP is in a position to win even without the USA in the war.