Something like this? http://architectural-model.com/
I don't know about USA, whether there are specialist model shops, but you've gotta have a lotta cash for what you want.
My suggestion would be to look up some woodworkers in your area, & see if they can build you one for cheap (they could build it out of plywood). I personally know people who have made miniature houses/landscape for a model museum & it's not too difficult. You just need the right tools, such as a jigsaw (an electric saw, not a puzzle) & small, sharp knives for cutting precison.
You could try doing it yourself. I'd suggest with cardboard. Look at pictures of buildings & try to replicate them exactly. It isn't difficult, you just need to experiment with paint colours to get the right shade for your building.
Of course, BE CAREFUL with any tools & if you're younger than 15 then you need supervision.
An alternative would be to learn a 3D program & create a city - e.g. in Spiderman & Daredevil lots of the city shots are 3D - & on here, DXM & Nightcast both have animated cities.