Mahonia, possibly Mahonia bealei but there are many...

Agreed.

Yes, birds like it. And that is likely how it is spreading and becoming an invasive in many states. It's not really a problem here in Northern VA, but I understand it is further South.

It's a very spiny shrub and probably useful in some landscape situations.

'....probably useful in some landscape situations.' In climates where it is not a problem re-seeder it is a highly appreciated shrub for its architectural foliage and its deliciously fragrant yellow flowers borne in mid-winter and very early spring. The spines are not a problem except for pruning and then no more that pruning a rose or holly bush. It and various other Mahonia species and hybrids are common and valued shrubs in the UK.

Here is a link that might be useful: Mahonias

Thank you everyone! Mahonia bealei looks EXACTLY like what I have. I think it's a keeper. :)