@thedoctor yep, I'd say just don't bring earthworms anywhere -- although I've never really tried to myself, I've just said "oh there's an earthworm! That's good." 😄
@thedoctor leaf litter is just decomposing plant material, that compose the top layer of soil, at least naturally. It's the soil that tends to collect at the top of the ground, and is part of putting nutrients back in the soil.
@thedoctor your mulch may come with invasive earthworms, which will eat your leaf litter. So that'd be a shame. But I'm not sure there's much to do about it! Earthworms are generally nice, but it sounds like don't *help* them propagate. 😅
Be careful not to spread earthworms in native US plant areas. They come in mulch, potting soil, etc. Raking or blowing leaves concentrates their eggs, which can wreak havoc in an area. Aapparently! -US Forest Service