I don’t agree that you, in Europe, can treat 1492 as the cut-off date, before which a species, that you had in any part of Europe before that date, could be called “native” to that area, in the way we, in the Americas, can use 1492, when the first European, Columbus, arrived with the beginning of world shipping, can treat a species found in any given area of the Americas before that date, as native to that area. Columbus, and following Europeans, had the goal of profiting from bringing materials to Europe, and moving materials, from around the world, to and from the Americas. This was the date, after which, there was regular transport of people, and materials, back and forth between the Americas, and the rest of the world, with, I expect, a majority of the species transported to the Americas unintentionally, as a byproduct of that global transport of people and goods. It was also after this date that people and materials were moved around within the Americas, at a rate they had never been moved here before, also largely driven by monetary profit. The species that arrived, from the rest of the world to new communities in the Americas, have mostly negatively the affected the American natural communities they weren’t co-evolved with.
I also expect even those species that arrived with the earliest European shipping, say 400 - 530 years ago, mostly still largely continue to negatively affect American natural communities that were not co-evolved with them. There would of course would be some percentage of the earlier immigrant species no longer doing net harm to American natural communities, and exceptions that are now needed by earlier community members that have come to depend on the immigrant species. Many older immigrant species could have already done the majority of their harm, and are less of a threat than newer immigrants.
And, no doubt, the first humans arriving from Asia tens of thousands of years ago, or later Native Americans, or the Vikings, could have transported species before 1492 that negatively affected the communities they were brought to, but that process was much less, and much slower, than the world shipping that came with the Europeans, and I believe that shipping driven by monetary profit, (unlike the American Indians with no monetary system) sped up the process. The slower process, mostly a longer time ago, of transport of fewer species, by the American Indians and Vikings, would have allowed local communities, to which they were brought, more time to adapt to them.
No doubt you have some species in Europe that were transported by humans before 1492, that to one degree, or another, have since become co-adapted with pre-existing community members, and to some degree have co-evolved with preexisting local community members, and are no longer presenting net harm to the communities they arrived in, but I expect many, to most, of those are still negatively affecting local community members that were not co-evolved with those immigrant species.