This sounds right. Just remember, the US Army of 1918-1919 was basically the creation of Congress in 1916-1917. Before that, it was designed to fight people like Pancho Villa and was nearly 100% on horseback. The Indian Wars were not far removed from this army which existed as a skeletal force up until that time. I’m pretty sure that Congress had no desire to create a large standing army at the time which is why it was rather quickly demobilized after the German surrender.It was less the size of the US army in 1919, but the size of the US economy that made it a potential force for stability on the European political landscape. (Consider how everyone, not least the other victors of the war, were in hock to the US thanks to plentiful wartime credits from the US.)
That, and the better prospects of the US army acting as an acceptably even-handed arbiter between the Germans and the French – rather than how the situation ended up, with France by default put in the position of providing the military muscle of the post-war settlement. Which wasn't a problem of the amount of muscle, but rather a combination of the attitudes of the French to the Germans, the Germans to the French – and the British and Americans effectively not accepting a situation where France would be free to enforce the post-war settlement by force, and so sabotaging the French.
Already before the Great Depression knocking over the politics of post-war Europe, the situation was a mess.
I've yet to see someone seriously fault the US post-WWII 1945 decisions to stay engaged – and that was based on the lessons learned from the decision to disengage in 1919.
It might have worked better at the time to send an army of occupation to Germany following the Great War but for reasons I have never understood, this did not happen. The result was that the German High Command could throw sand into the eyes of its own population and make the absurd claim that they hadn’t lost the war. They did lose the war.
Why the British and the French could not send an army of occupation to Germany is a mystery to me. It really wasn’t the job of the Americans to do this then, but it might have worked out better if they had stayed. US voters would not have agreed.