I had no idea there was a population of feral European rabbits in Duluth--very interesting!

I don't think that European rabbits can hybridize with eastern cottontails--I don't know 100% sure, but I haven't found anything indicating they can, and usually animals in different Genera (European rabbits are Oryctolagus cuniculus) can't interbreed. I won't say they never can, because there is some evidence that mallards can hybridize with ducks outside of their Genus.

Thanks for the very cool information!