Meh with non-native cats over here gone the native cats would do the killing. The reason we spay strays is more to protect wildcats against c competition, they're not interbreeding much but long-term it's a concern.

Obligatory picture and another yes they do look quite like domestic ones. Behaviour is quite different, though, particularly they're impossible to domesticate. Behaviour you'd consider severely fucked-up cat psychology in African wildcats (which are the ones who domesticated themselves by moving into grain storages) are par for the course for European wildcats. They're not asocial, they're not broken, they just hate humans.