Was Germany seemingly facing defeat or were they realistically about to take Paris, and if so would they have likely have been able to force a more favorable peace?
Where were they in terms of manpower/military equipment at that point as compared to the Brits and French? What was the general direction of the front lines moving in the few months prior to American involvement?
I hope this isn't too much of a historical what if as of course anything could happen, but there was a big debate on a TIL about it and I'm curious how the community here sees it.
Is there a better way to look at this question?
America declared war in April of 1917, and I think their major involvement (i.e. 'boots on the ground') began in February-April of 1918.
When America first declared war, things were going reasonably well for the Germans. Russia had signed an Armistice several months before, meaning that the Germans could finally focus their men and material for an offensive in the west. In the west, the German Army was resisting the Nivelle offensive and the attacks at Arras, as well as establishing a brief air superiority over the Allies. It might be a stretch to say they were winning, and I don't want to fall into the old "defenders had it easy" myth, but I think the Germans had a realistic shot at winning the war at this point.
This situation changed fairly drastically when the U.S. entered but, generally speaking, it meant that the window for a German victory was closing due to the fresh manpower and material. I might as well note that the material contributions of the US are a bit exaggerated, despite what you may have heard about the Liberty aircraft engine. Nonetheless, had the war gone on longer, America's manufacturing sector would have been a major advantage to the Entente.
Additionally, America's entry inspired two of the most iconic offensives of the war: the drive towards Passchendaele and the German Spring Offensive. One of the main goals of Passchendaele was to secure better ground from which to launch an offensive. This was a minor objective to the the overall goal of the offensive (sweeping through Belgium to win the war). It inspired the Spring Offensive for the reasons I mentioned above: the Germans saw the window of victory closing, so they decided to throw what they had at Paris end the war. American forces were vital in stopping this offensive, mostly due to the fresh manpower I mentioned above.
Finally, I've heard it argued that Churchill claimed that the two sides were preparing for peace in 1917 since neither side saw decisive end to the war in sight. America's entry shut down these early talks by giving the Allies an opportunity to really win the war. Sort of in "What If" territory, but that seems to be the direction of OP's question.
In terms of equipment: the Americans were generally behind the rest of their allies. Very little aviation, tanks, machine guns, or other things useful in the technology heavy war. The American SPADs, S.E.5as, and Renault tanks were all provided by the French or British.
Even in terms of small arms, the famous Springfield M1903 and M1911 pistol were in fairly short supply. American troops were often supplied with the M1917 "American Enfield," which was a British design (not related to the SMLE, by the way) retooled to fire American ammunition. For pistols, many secondary or reserve troops were issued the M1917 revolver. For more on American preparation for the war, see how many American weapons are called the "M1917" (I can think of two more off the top of my head).
So American entry changed the war pretty drastically, mostly at the strategic level by forcing the Germans into an offensive and providing the Entente with more soldiers, which increased the odds for the 100 Days offensive (the counter offensive to the German Spring offensive) succeeding. The material advantages of having the US as an ally were not really seen in World War One, but it may have been a factor if the war had continued much longer.
Edit: the Netherlands was unoccupied during the war.
Sources:
"A Storm in Flanders" by Winston Groom
"The Great War in the Air" by John Morrow, for the American material contributions
"Passchendaele: The Untold Story" by Robin Prior and Trevor Wilson
"The Gun" by Chivers, for the American small arms info.
I found this threat that is really enlightening on the subject. I'm still trying to dig through it and am hoping there are other comments that can inform on this from different angles, but anyone interested should probably take another look there too.