Cars kill 1000000x more than cats. If you care about wildlife, that's where you'll put your dent.
I have 3 outdoor cats. The older 2 take out 1 mole, 1 mouse and 0.3 birds a week. Combined.
The younger is a terror tho. 2 birds, 2 moles, 2 mice, a week.
Rural
Yeah, it's pretty fucked up