Domesticated cats as an invasive species?

https://daily.gazette.com/article/282175064871105

This article talks about a scientific institute in Poland that recently classified free-roaming cats as an alien invasive species. As you can imagine, it stired up a lot of controversy. There have been countless studies and data that support the fact that free-roaming domesticated cats have caused the population decline of many birds and rodents in this country. In fact, in New Zealand there is a concerted effort to contain the feral cat population because of the damage they are causing to native animals.

Many cat lovers who are advocates of letting their cats roam outside find issue with this. The article in the Gazette quotes a veternarian who argues that humans are actually the biggest invasive species.

What do you think? Are free-roaming cats as a threat to the ecosystem as some people claim they are?