Princess' Crusade. American Imperium Trilogy

After nearly a generation the city-state of Knoxville is beginning to thrive following the collapse of the United States. However, its closest outlet to the sea, the port of Savannah, over the mountains and downriver, is occupied by the Chinese Army who impose crushing tariffs. The city fathers have only one person to turn to for help. Growing up trained by her military father and with a nervous system vastly modified by the Thinking Machines, Faustina Hartmann builds a private army of two brigades - called legions - to march on the Savannah garrison and liberate it, for her city and herself.
But the Chinese have many technological advantages, not the least of which is their orbital bombardment battle station. Calling herself demi-human, Faustina's ambition far outstrips the liberation of one port city. As the interior of America comes back to life it will need a strong guiding hand and she sees that hand as her own.