www.people-press.org

The Pew Research Center for the People and the Press provides comprehensive access to survey and polling data related to US foreign policy.

polidata.org

Provides reports on both election and polling data in the US in terms of geographical distribution.

https://www.brookings.edu/project/red-and-blue-nation/

This Brookings project ‘Red and Blue Nation’ explores divides in the United States, with links to numerous articles on the red/blue divide.

https://www.foreignaffairs.com/articles/united-states/2007-07-01/grand-strategy-divided-america

Foreign Affairs article on Grand Strategy for a Divided America by Charles Kupchan and Peter Trubowitz.