Flynn, Michael F. "Forest of Time"
Divergence: c 1765 CE
What if: The US never united, resulting in a collection of independent States fighting constant border wars.
Summary: A crosstime traveler is stranded in a Wyoming Valley where Pennsylvania is fighting for control vs Virginia and New York.
Published: In Analog, June 1987; The Forest of Time and Other Stories, Tor 1997 (0312855265BUY), Tor 1998 (0312865872BUY); and Roads Not Taken: Tales of Alternate History (eds. Gardner Dozois and Stanley Schmidt), q.v.