Crop subsidies are certainly poorly applied and poorly distributed, but we also need to not throw the baby out with the bath water. Crop subsidization is the only alternative to the granary system, which while decent still resulted in repeated famines for thousands of years basically everywhere, while no country that has decent crop subsidization ever has famine. Crop subsidization in general makes granaries 90% obsolete because you always aim to over produce crops and so even in bad years you still produce enough food despite the unexpectedly low yields. It also makes food prices WAY more stable so that a bad July doesn't cause wheat prices to double because there isn't enough to satisfy demand. It is really the only way to ensure you always produce extra food in a capitalist economy because otherwise margins are only like 2% while crop yields can swing 30% even without extraordinary weather events or storm damage.
I do want to note though that corn is possibly one of the least useful crops to subsidize, it is one of the most robust and predictable food crops we grow, which is why so much of it is grown despite a large fraction of it's energy going into worthless stalk. More delicate crops that have larger and less predictable yield swings, like wheat, or something with delicate fruits that can't be stored long, likely deserve the majority of subsidization money that currently goes towards corn.