[flusensieb]

Some rivers (especially in the US) miss their waterway-line through lakes/reservoirs and the part crossing the dam. These need to be added.

Edit: https://wiki.openstreetmap.org/wiki/Rivers Explains it quite well with some graphics.

[rmc]

(I'm the creator of this) Yes lots of rivers are missing those sort of connections through lakesᵉᵗᶜ, but that's not unique to USA. Please keep mapping to fix up things.