There is an actual Willamette area but it's in Oregon, not Colorado. It's not clear why Capcom decided to give it a shout out, though it could have to do with being the final destination in The Oregon Trail games. They say the name wrong, however.
One of the stores in the Willamette mall is a small theater called Movieland.
Even the seeming anvil about mall walkers/consumption culture being no different than the zombies is straight from Dawn of the Dead.