Native Culture Areas of North America - Game Information

And of course, physiographers generally don't use such vague terms as "Northeast" and "Southeast" to begin with, preferring more specific language.

Many of these terms have several meanings depending on context...

Just to note:

These regions do not correspond well with standard physiographic regions. In general these regions are fewer and larger than regions used by physiographers.

For example, mostly we don't think of the "Northeast" as including all or part of Indiana, Illinois, Iowa, Wisconsin, Minnesota; the Plains are generally not meant to include the surrounding areas (notably, most of the Rockies); and so on.

More information here (including the map):

http://en.wikipedia.org/wiki/Native_Americans_in_the_United_States

The map alone:

http://en.wikipedia.org/wiki/File:Nordamerikanische_Kulturareale_en.png

The author has released this image into the public domain.