Pirates have to fight somebody.  Given the real history, you had French pirates operating out of New Orleans who attacked British shipping but not US shipping.  Who do you think supplied the cannons that Andrew Jackson used to defeat the British in the war 1812?

English privateers were given a letter of marque and reprisal authorizing them to become commerce raiders.  Spain was richer than England.  At the time of queen Elizabeth the first of England, Spanish commerce raiders would have had slim pickings.  :-)

I think your husband is reading into the story more than Jim Butcher has written.  If it helps, think of the Aurorans as French.

Besides, the divisions between the spires will disappear when they have to face the common enemy.