a good way to improve those odds is Kaiser Wilhelm keeping Bismarck around as long as possible.The US had little enough to fight over with Imperial Germany. Aside from my Great Grandfather being a Swabian draft dodger from the Franco Prussian War. It was rather inept German diplomacy and British skill that brought the US in. Really the default scenario is US neutrality. To gert the US in as a Central Powers ally, its necessary to reverse the diplomatic situation. The Brits and French blundering at every step & the Kaisers Foreign Office blandishing with skill & finesse.