It depends what you mean by outrageous. Invading a neutral country, whose independence you had yourself guaranteed in writing was generally considered outrageous by the morality of the time. Shooting devoutly religious English nurses as spy's, was typical of the Germans' behaviour, but was probably justified under international law - does this count as outrageous? Then you have the frequent arbitrary atrocities which I assume you mainly refer to.
The atrocities in Belgium DID have a major influence on American opinion, both because of reporting on them and because Americans volunteering abroad saw them and told their friends and family. The taboo on invading other countries resulted from the world wars; it did not precede them. Countries in Europe had been periodically invading other countries in Europe for a long time before the Great War and the average American did not give a sh!t. The USW issue is pretty difficult to separate from the issue of supplying weapons to the Entente, and a large part of the support for supplying weapons to the Entente was a result of the Rape of Belgium.
Rubbish. Invading another country with a plausible pretext perhaps wasn't a taboo, but doing it with absolutely no pretext and to a country whose neutrality you had specifically guaranteed, certainly was.
The US was not a signatory to that treaty. Britain was, but Britain was not the US. Europe had seen the Crimean War, the Austro-Prussian War, the Franco-Prussian War, various Balkan wars, various Italian wars of unification without the American public taking sides. Even during the War of 1812 the US didn't care about the defeat or victory of Napoleon.
The events are so close together they are really hard to separate. As I said the invasion of Belgium itself was an 'outrage'. My contention is that this, along with the myriad of other reasons, was part of why the US favoured the Entente. Would it be less to some degree without the German atrocities in Belgium? Almost certainly. Does it really change the outcome the war? Of course not. The Lusutania is still sunk, the Germans still make clumsy attempts to bomb British civilians presumably, and crucially, unrestricted submarine warfare is still resumed and the Zimmerman telegram still sent.
Well, I certainly think that getting Germany to invade Belgium without committing atrocities would be harder than simply having it go east first, but the OP specifically asked about a Germany that invaded Belgium without committing war crimes.
A misdeed? Perhaps. One that outweighs suspected state-sponsorship of terrorism? No. One America need be concerned with? No.
Well the Anglophilia and Francophilia would certainly still be there.
That's assuming that the USA still backs the Entente and that a Germany that didn't commit war crimes in Belgium would still pursue unrestricted submarine warfare and send the Zimmermann telegram. None of those things are certain.
On the other hand, the Entente went and did a similar thing to Greece when it tried to enforce its neutrality. Vaguer principles like neutrality were kinda something whose violation only mattered if it was done by the enemy. German atrocities were the main difference, and they were the primary basis for Entente outrage. Invading Belgium was bad, but what was done in Belgium was what was more on people's minds. If the Germans had gone through Belgium without committing atrocities against civilians, your average Briton or American wouldn't really have cared.
Two rules
