If you're in the western half of the country, Alaska is essentially always a route for wherever you want to go, whether staying west or going east.

If you're already on the east coast and aren't going to the west coast, then Alaska doesn't have a route. So I suppose they are "regional", where the region is about 70% of the country rather than all of it.

You don't have to go to the east coast to have trouble finding them. In St Louis they have a whole 4 flights, and 3 go to the west coast. So yes, absolutely regional. And that's the western side of the midwest. In comparison, Southwest has 55 direct destinations from the same airport. This isn't cherry picking: You have as sparse a route map from Dallas, yet another non trivial city. From there, Southwest has 70+ direct flights.

So yes, still a regional airline if your home base isn't exactly on the west coast.