The post you replied to
questioned whether they were considered invasive everywhere and
asserted that they were on a global list of the 100 worst invasive species.
All as counter to the claim that Australia was unique in considering cats a nuisance.
It seems that assertion is true:
38. Felis catus
Felis catus was domesticated in the eastern Mediterranean c. 3000 years ago. Considering the extent to which cats are valued as pets, it is not surprising that they have since been translocated by humans to almost all parts of the world.
Notable predators, cats threaten native birdlife and other fauna, especially on islands where native species have evolved in relative isolation from predators.
Common Names: cat, domestic cat, feral cat, Hauskatze, house cat, poti, pusiniveikau
GLOBAL INVASIVE SPECIES DATABASEhttp://www.iucngisd.org/gisd/100_worst.php
Is there nowhere in Europe where cat populations are kept in check to protect birdlife and other local native species?