nationalatlas.gov is an amazing resource. It is stocked to the brim with US maps displaying everything from political boundaries to annual precipitation to, yes, invasive species. The interactive Map Maker application lets you view distribution data for a variety of invasives, and even lets you play around with overlaying different maps. I think I see a correlation between purple loosestrife distribution and toxic releases...just kidding.
Thanks to Zelda at Mute Complications for sending in this excellent link.