You missed a couple important factors.
Fuel contains hydrogen sulfides.
A correctly functioning catalytic convertor converts these hydrogen sulfides into sulfur dioxide (SO2).
Sulfur dioxide reacts with moisture to create sulfurous acid (H2SO3), then oxidizes in the atmosphere into sulfur trioxide (SO3). This further reacts with water to create H2SO4- sulfuric acid. This is the major cause of acid rain, and acidification of the environment.
The takeaway?
Catalytic convertors themselves are killing the environment.
Politicians (EPA) arbitrarily came up with a short list of pollutants (carbon monoxide, hydrocarbons, and nitrogen oxides) and mandated the use of catalytic convertors to convert those three pollutants into "less harmful" (re: non-regulated) compounds.
The incidental creation and introduction of sulfuric acid (and other chemicals) into our environment through the use of cats is something that has long been downplayed, since that would call into question the wisdom of our politicians (pretending to be engineers) who mandated this...
Not to mention the social and environmental impact of mining/processing/refining the platinum, palladium, and rhodium required for the manufacture of catalytic convertors... but that is a whole other discussion.
Follow the science, not the "We're all gonna die/humans are evil/donate today" docudramas.
Humans aren't evil, but we can be pretty stupid at times and be our own worst enemies.