NEW: Smoke from hundreds of Canadian wildfires is spreading across the United States, with air quality expected to reach unhealthy levels for millions of Americ

NEW: Smoke from hundreds of Canadian wildfires is spreading across the United States, with air quality expected to reach unhealthy levels for millions of Americans. [▻](https://video.twimg.com/amplify_video/2077349605562359808/vid/avc1/1280x720/lWV8ESuMTZk5l4Q0.mp4)