What are the steps did US take to prepare for World War 1?
There were very few steps taken by the US to prepare for war, before the US actually declared war in April 1917. President Wilson had told the American people that they must remain neutral in thought as well as in deed. There was no increase in the size of the military branches, no training, no designing or ordering equipment, no money made available for those purposes. It had always been the policy of the US Army to send promising young officers as observers whenever there was a war going on somewhere in the world, so that US officers could learn from their reports the latest wrinkles in their profession, as forged in the crucible of war. Wilson allowed no observers to be sent to soak up the knowledge of the current state of military art.
Since about 1907 the US had been engaged in the international arms race of the day, which meant building two or four new battleships each year. These were the largest ships of the time, but few smaller vessels were built. Though the US had invented powered flight just a few years before the war and there had been a full-scale air war in Europe for at least two years, the US possessed at the time it entered the war perhaps four airplanes capable of front-line service in France. The navy had a few pilots and some seaplanes, and the army's aviation was a section of the Signal Corps. This was embarrassing. So the US set out to build an American plane, the JN-4 "Jenny". This was a two-seater observation type, of the sort used on the Western Front for scouting over enemy lines to find targets for the artillery. It was not a very good plane and few saw any service in France. The Jenny is best remembered as the plane flown by "barn-storming" pilots after the war, who had bought them surplus from the government. They flew from pastures around America and popularized aviation, giving rides to many boys who went on to fly in WWII. The US also set out with great fanfare to build an aircraft engine, the "Liberty Engine". This was a design borrowed from the Europeans, already obsolete, too heavy and producing insufficient horsepower for front-line service in France. The Liberty Engine is better remembered from the post-war years as well, when boat builders bought them surplus and installed them in fast boats, rumrunners, used to smuggle in liquor during Prohibition.
One useful step the US did take before getting into the war was to set up "Plattsburg Camps". These were named for the first one, at Plattsburg, New York. These were camps, strictly voluntary, where young men could go for a summer of military instruction, something like the Officer Candidate Schools of WWII, though giving nothing like the good training the "90 day wonders" of the next war would get. It was better than nothing. To field a massive army such as those contending in France, the US would need thousands of junior officers, to be platoon and company commanders. There was no ROTC in those days, and the US Military Academy graduated only a few hundred junior officers per year. There were a few military colleges, such as VMI and The Citadel, which also turned out men with military training, but this was a drop in the bucket compared to the need.
The "Punitive Expedition" into Mexico in 1916 gave some units, regular army and National Guard, some experience with camp life and military routine, but chasing bandits around the desert of northern Mexico was nothing like trench warfare in France.
When the war started several of the large American civilian firearms manufacturers had signed contracts with the British government to supply several million rifles. These were to be the standard British rifle, the Lee-Enfield, in .303 caliber. These companies still had the machinery and were able with little trouble to change the size of the bore and the chamber to make these rifles in the standard American caliber of .30-06. These rifles were called "American Enfields" and more US troops were armed with one of these than the standard American rifle, the 1903 Springfield. The Springfield Arsenal turned out only a few thousand of these per month, nowhere near enough to equip millions of men, and production had not been stepped up before the US got into the war.
About all America was able to give her soldiers was uniforms. Everything else they had or used was supplied by Britain or France. All artillery and machine guns, and automatic rifles, hand grenades, trench mortars, gas masks, airplanes, and tanks were all provided by one or the other.