I thought this was quite an interesting report, released from mobile advertising company Jumptap.

...consumers in the South and Southwest tend to be Android-biased compared to the rest of the country, while those in the Midwest and Northeast lean towards iOS. California, Texas and Florida over-index for Android use and states in New England and the Midwest over-index for iOS use. Blackberry use, which over-indexed in New York, was also included in the geographic data. This new data establishes an evolving narrative of a North vs. South divide in the ongoing battle of the two top mobile operating systems.
You can download the report by clicking on the link at http://www.jumptap.com/jumptap-mobile-stat-report-maps-the-us-as-android-vs-ios/