The US is not helping out because it feels sorry for Ukraine, it is because the US does not believe Russia would stop at Ukraine, and would press on to the other former territories of the USSR and it’s allied countries, several of which are in NATO.
The US is sending munitions to Ukraine now because they have a population willing to fight, and if Russia escalates, that will involve sending US troops to protect NATO countries. We are bound by treaty to do that, as long as an idiot President doesn’t find a way to leave NATO…