If you're talking about "The Guess Who" version of American Woman, it wasn't a pedal at all, it was a small amp plugged into a bigger amp, the first (but primiative) and very effective "overdrive".

The guy's name is Gar Gillies out of Winnipeg Manitoba, he built an amp for Randy Bachman called the "Herzog"

Here is a picture of Randy with one of the Herzog amps:
http://www.randybachman.com/index.php?choice=2¬e=2

from Randy Bachman:
"The signature guitar lines in "No Time" and "American Woman" were my '59 Les Paul (neck pickup), into a Herzog, into a Garnet Amp."

More Info:
http://www.garnetamps.com/PPbyM.htm
http://www.lynx.bc.ca/~jc/garnetAmps.html