Countless places across the United States still bear the name of Alexander von Humboldt — queer traveler, visionary naturalist, now largely forgotten. The longing filmmaker uses three of them as unlikely common ground, weaving Humboldt's own words through present-day lives: urban activists greening neglected neighborhoods, scientists scanning redwood forests, hunters returning bighorn sheep to protected land. Across generations and landscapes, HUMBOLDT USA asks what remains of a vision of "interconnectedness."