if it wasn't hummingbirds, I would say we have a "butt-ton", but since it is hummingbirds, I'll go with "many".
The most common species is the Ruby-Throated Hummingbird, which ranges over the most populous areas of the country, including most of the East coast and through Quebec-Ontario-Manitoba-Saskatchewan-Alberta. Basically from the foothills of the Rockies to the Atlantic, south of about 55° north.
Putting out feeders is common, and gets nearly instant results.