how do i get nationwide search
On the search form, right below the ZIP button is a RADIUS button, just scroll down to "nationwide."
The Car Gurus new car search is limited to a 500 mile radius but used cars can have a nationwide search. Other search engines such as Cars.com might allow a new car search nationwide. You can always use a zip code for another city to expand your search.
So it does... my bad. Here is a little hack that works, do your new car search with "500" selected for radius. Then when the search results page comes up, scroll right in the URL (the web page address bar) to where you see "distance=500", and then add another zero to that and hit page refresh. You know have search results for a radius of 5000 miles. I tried this (living in Ohio) and got results for Hawaii, California and Arizona, so it seems to work.
Clicking on radius for used cars only goes to 50mi, and when nationwide is listed clicking on it does nothing.