Wildfires release large amounts of ammonia, a gas that can affect air quality and contribute to nitrogen pollution when it deposits back to the surface as ammonium. The effects of wildfire smoke on these pollutants over large regions are not well understood. We examined how the record-breaking 2023 Canadian wildfires influenced ammonia in the air and ammonium in rain across the Upper Midwest and the United States. Comparing 2023 to the previous decade, ammonia levels in the rose at most monitoring locations, and ammonium in rain increased at more than half of sites nationwide. The Upper Midwest was especially affected, with most sites showing significant increases in both pollutants. Aircraft measurements in a smoke plume over the Midwest in 2023 found elevated ammonia and ammonium alongside other wildfire smoke tracers. Our findings show that extreme wildfire seasons can disrupt air quality and nitrogen cycling, which has implications for ecosystems, human health, and how we model the atmosphere.