I think I got it.

Taking out “mortal engines” definitely helped. Bing clearly doesn’t understand that it’s a movies with a specific style.

I finally thought of saying the machine is made of buildings, and that is a post apocalyptic world.

The prompt was: an enormous, wide, steampunk machine with no obvious power source, made of are several landmark buildings of Sacramento. it is moving at high speed across the countryside on huge mismatched wheels. trees seems small next to the hulking structure. dust rolls from under the machinery to indicate speed as it rolls across the post apocalyptic terrain