"The Pugnacious Peacemaker" is Harry Turtledove's sequel to L. Sprague de Camp's "The Wheels of If", a classic novella of alternate history depicting a North America which had been settled by the Vikings of Vinland. It was first published in Tor SF Double No. 20, Tor, 1990, along with a reprint of the de Camp work. Both also appeared in Down in the Bottomlands and Other Places by Baen in 1999.
"The Pugnacious Peacemaker" picks up a year after "The Wheels of If" ended. Cross-timeline immigrant Allister Park, alias Judge Ib Scoglund, an international judge, is tasked with negotiating a border dispute between Tawantiinsuuju (a longer-lived Incan Empire) and the Emirate of the dar al-Harb (located in OTL Brazil).
Park/Scoglund's method of conflict resolution is similar to Basil Argyros, central POV of Agent of Byzantium.
In Gunpowder Empire (Crosstime Traffic Series volume 1), it is related that Crosstime Traffic patrols an alternate where North America was colonized by Vikings, but no further details are shared.
In Through Darkest Europe, Muslim people colonized large parts of the New World. "Islands in the Sea" and In High Places (Crosstime volume 3) see Islam spreading through much of Europe.