What things were rationed during World War 2 in America and why were these things so hard to obtain?
Rubber (tires) it was being used in military equipment.
Gasoline, same thing. Tanks, airplanes, jeeps... all of the military equipment was using gasoline.
Silk, formerly used in ladies stockings, was being used for parachutes.
Sugar, was being sent to the military in packaged foods.
New automobiles were not being built during the peak of the war. Entire production lines had converted to build military equipment.
People were generally willing to do without in an effort to send more to the military.
Many things were rationed, food, water, weapons, etc.
Water was not rationed. Potatoes were not rationed because they were plentiful in the USA but in England they were rationed. Depending on which country or area where you lived pork meats were not rationed. Things like salt. baking soda, spices, vanilla, baking powder were not on the ration lists. Some medicines were not rationed but antibiotics and medicines needed in the war front were rationed amongst the medical facilities. In the USA some vegetables…
You need to specify a country and a time. There's a widespread misconception that specific goods were simply either rationed or not rationed and that the amount(s) allowed then remained constant throughout the war. The tendency in all coutries was for more and more things to be rationed, and for the amounts allowed to be reduced. In Britain, for example, bread was not rationed during World War 2, only afterwards!
Rationing means to control, limit, or reserve the amount of something (usually a good) that someone or some group can have. During the Second World War, for instance, things such as butter and sugar were rationed so that there would be enough for everyone to have a little. In Britain, tea was rationed.