Do you know some utility or a web site where I can give US city,state and radial distance in miles as input and it would return me all the cities within that radius?
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Take a look at this web service advertised on xmethods.net. It requires a subscription to actually use, but claims to do what you need.
The advertised method in question's description:
GetPlacesWithin Returns a list of geo places within a specified distance from a given place. Parameters: place - place name (65 char max), state - 2 letter state code (not required for zip codes), distance - distance in miles, placeTypeToFind - type of place to look for: ZipCode or City (including any villages, towns, etc).
http://xmethods.net/ve2/ViewListing.po?key=uuid:5428B3DD-C7C6-E1A8-87D6-461729AF02C0