As the Central Valley’s flatlands give way to the rolling hills of California horse country, this quiet city that calls itself “the Cowboy Capital of the World” and features weekly rodeos seems but a blip on Highway 120, halfway between San Francisco and Yosemite National Park. But Oakdale, a city of about 22,000 people in Stanislaus County, is facing a new and frightening renown: A few miles from downtown, Nathan Damigo, one of the most prominent new white nationalist leaders in America, runs a group that helped organize last weekend’s bloody rally in Charlottesville, Virginia.