There are a couple different kinds.
The ones you have down in the south are probably more native than the ones up here.
They break down material into nutrients...but you have to have material in the soil to begin with..
https://ecosystemsontheedge.org/earthworm-invaders/
"It’s an ironic truth—the traits that make earthworms wonderful for gardens are the same ones that make them dangerous for forests. Earthworms stir up the soil, making nutrients more accessible to flowers and vegetables. But plants in forests have evolved other ways to get nutrients from the ground. When earthworms convert them into easier-to-access forms, it can favor invasive plants that later take over the understory. In the process they have also been known to endanger birds and orchids. They can be a threat to humans as well, collapsing irrigation ditches and speeding up erosion."