OK, somhow the genre "American Gothic" fits perfectly to the music of the Pumpkins.
If you look at the albums, wether they are American, Gothic or both.
Gish - An American early 90s indie-rocker.
Siamese Dream - A (nearby) perfect American rock album with some sad moments (Gothic?!) in it
MCIS - Both off the two worlds; American rockers but also silent and gothy moments of sadness and lonliness.
Adore - Guess, what
MACHINA I & II - OK, you can call this an experimental set of songs, but in it's depth, I think, there's much more desperation and helplesness than on every other Pumpkins release (Stand inside your love, In my body, Age of innocence...). So for me, the whole MACHINA-thing has the gothic-intuition in a subliminal way.
Well, that's just how I could understand Billy's statement.
...and yes, I know, classic gothic is something very different (Some friends of mine go in that gotic-direction) and the Pumpkins
ARE no gothic band (especially not today), but there are parallels and I think in mid 90s Billy felt the same kind of lonliness, loss and maybe longing for an end, too, as gothic people claim to do.