You could try thinking about it. Buying cat food at the store isn't magic. It comes from somewhere.
Cats can eat the wildlife in your yard. Or, you could have wildlife in your yard, and offset the calories by growing them on more farmland somewhere else.
The only difference in the second scenario is that you don't see the extra acre of woods — along with all the lizards and birds that would live there — getting turned into soybeans.
"Feral Cats are wild-living variant of the common pet cat, introduced to Hawai‘i by Europeans. Feral cats have established populations on all eight of the main Hawaiian Islands and contribute to widespread ecological disruptions that threaten native Hawaiian wildlife. Feral cats are one of the most devastating predators of Hawai‘i’s unique wildlife. In addition to direct predation, feral cats also spread a potentially lethal parasite (Toxoplasma gondii) that contaminates terrestrial, freshwater, and marine environments and has been shown to negatively impact birds and mammals – including humans."
Most pet food is made from waste from producing human food. E.g. offal. So I'm not sure pet food accounts for any significant loss of wild land on its own.
Cats can eat the wildlife in your yard. Or, you could have wildlife in your yard, and offset the calories by growing them on more farmland somewhere else.
The only difference in the second scenario is that you don't see the extra acre of woods — along with all the lizards and birds that would live there — getting turned into soybeans.