I’m writing a Godzilla fanfiction and in it, after Godzilla rampaged across the West Coast and is making his way further inland, the US Government initiated the mass evacuation of over 50 million people across Washington, Oregon, California, Nevada, southern Idaho, and a small bit of southwestern Arizona. The goal is to get as many citizens as possible across the Rocky Mountains into refugee camps located in the Midwest.

Is it at all possible for the government and military to evacuate that many people across six different states? What would be the individual, intricate details behind the logistics of such a feat?

Assume Godzilla rampaged the West Coast in to a fine powder and is moving east, into the western states of the United States (Washington, Oregon, California, Nevada, southern Idaho, and a small bit of southwestern Arizona).

How would the US Government evacuate the 50 million Americans to refugee camps located east of the Rocky Mountains in the Midwest? I'm really interested in the logistical details.