In addition, most US contributions are done in the form of donating surplus/outdated military equipment that was manufactured by the US defence industry decades ago, at a fictional list price.

And yet, way too many Americans seem to think that each billion-dollar contribution the US has done to Ukraine consisted of someone taking that money out of the US treasury now and giving it to Zelensky as a sack of cash or something.

No, the money left the US treasury many years ago, and went to US defence industry. The aid bills also typically contain an agreement for future spending on US defence industry to replace the donated equipment. In each case, the tax money went to US companies in the MIC, and it is quite something to see how so many people on the right wing now thinks this is a bad thing.