Around here the best example of an invasive species changing things is purple loosestrife. It crowds out the cattails and there are a lot fewer redwing blackbirds around as a result. The plant also clogs waterways and affects things that way as well.
The birds aren’t on the edge of extinction or anything but the numbers have definitely fallen since I was a kid.
Come to CA,you will see all the red wing, and black wing, black birds you want and then some.