In my novel, New Rome Rises: Dux Imperatorius, Oklahoma City has a major role. It affects everything in the New Rome Rises series. Here is a description of the 1st book.

The new Roman Empire invades the American Southwest, and faces a new kind of U.S. Special Forces lead by a cowboy and a member of the U.S. Senate. They form an alliance with the last surviving member of the British Royal Family, twenty-two year old Owen Badon. In London Caesar’s sixteen-year-old daughter is torn to between her loyalty to her father and as the new Queen in the United Kingdom. All of this and more are in New Rome Rises: Dux Imperatorius. http://amzn.to/Ss2SFq

I hope this is something you will be interested in since it does include Oklahoma City and the west in general.