Wonder not:

https://community.openstreetmap.org/t/lake-ontario-lake-america/146975

Basically, OSM is a database containing points, paths, and polygons.

Each item can have any number of fields. Obvious ones like lat and lon, and specific ones like speed limit or entry fee.

An item can have many names, and its up to the renderer to choose which to show a user, or whether to show any.

The locale specific name for the US will change whenever the US govt department adopts the new name.

The general, most commonly used name will be lake Ontario until the most common make for the lake is lake America, which is unlikely to be ever.