It depends on the events that preceded US neutrality. We cant just say neutral US in 1917. A lot has to happen before that in order to make it possible
Isn't japan already in the war on the entente side? And if it is why does it need a 'Co-Prosperity Sphere' when it has unlimited access to the GB/FR empires. (+ informal sterling area etc)............Except- Japan. Japan probably gets closer to the US, needs the manufacturing expertise, needs the raw materials, needs the agriculture. Britain can rule the waves in the Atlantic and keep the US from trading with Europe, but can't in the Pacific against a combination US/Japanese trade if they were even willing to try to embargo the US or keep the US from trading with the Japanese, which the Japanese are Entente anyways. WWII in Europe can be butterflied, but this probably enboldens a stronger Japan to go after European colonies with a more friendly non-interfering US willing to maintain trade. Japan gets farther along before attacking the US which has to eventually happen unless Japan allows free and open trade between the US and Japanese Co-Prosperity Sphere and possibly some sort of implicit "Line of Tordesillas that keeps US sphere from Japanese sphere, but the Philippines exists and the US either gives it up for peace or the Japanese allows the US to have such a dagger at its heart, neither is going to acceptable. War eventually happens.
Isn't japan already in the war on the entente side? And if it is why does it need a 'Co-Prosperity Sphere' when it has unlimited access to the GB/FR empires. (+ informal sterling area etc)
https://en.wikipedia.org/wiki/Japan_during_World_War_IJapan joined the Entente relatively late. Japan will join the Entente just to take Germany's Pacific colonies regardless of what the US does, it's almost impossible to butterfly it away. That answers your first question.
Your second question about the co-prosperity sphere. For the exact same reasons it developed the co-prosperity sphere in OTL. I don't understand the question as it isn't asking a difference with the ATL, it's asking a question regarding OTL real history. I think you may have gotten confused in that I drew out the conclusion of what happens from 1914 out to about 1940. So the co-prosperity sphere talk was not about WWI, it was relatively the same period as OTL, in the interwar period. A US non-interference with WWI will have very little butterflies on Japan's history, regardless of what some people on this site like to think about any POD results in wiping out every single human who has been born after it and starting from scratch.
So...no loans to either side will hurt the Entente way more than the Central Powers, and if the USA tells the UK and France that if they don't allow at least "humanitarian" trade with CP, no war related material will be sold to them...
Your second question about the co-prosperity sphere. For the exact same reasons it developed the co-prosperity sphere in OTL. I don't understand the question as it isn't asking a difference with the ATL, it's asking a question regarding OTL real history. I think you may have gotten confused in that I drew out the conclusion of what happens from 1914 out to about 1940. So the co-prosperity sphere talk was not about WWI, it was relatively the same period as OTL, in the interwar period. A US non-interference with WWI will have very little butterflies on Japan's history, regardless of what some people on this site like to think about any POD results in wiping out every single human who has been born after it and starting from scratch.
My point was just that Japan will almost certainly join WWI early on, after that any lesser GB-USA relations only helps Anglo-Japanese relations think WNT negotiations and end of AJA, if they stay allies then Japan is free from any trade sanctions and can buy from GB (+ probably France) any commodities it wants and sell stuff for the European war?
Germany would be able to win. They just defeated the Russians and had the extra personnel and financial resources to overcome the Allies
The real issue is whether the lack of American reinforcements causes Allied morale to drop during the Kaiserschlacht. If it does, Germany can get a win as the Allies sue for peace during a panic.
However, it must be pointed out that it's mainly an issue of morale at this point. The US troops weren't really needed to prevent the Germans from taking Paris, but knowing the Yanks were coming did much to bolster morale.
Only after it was defeated in the field.If Allied morale doesn't collapse, Germany loses the war. There is a reason Germany sued for peace in Autumn 1918 even though the Allies had not entered Germany. It was because the home front had collapse and the German army in a mutinous mood.