Why does the film have no American film distributor? Because the American film industry pigeon-holes every film and script being marketed. If something
like your film did badly recently, that means your film will bomb too.
I'm marketing a script right now which involves a 1920's football story -- my agent is telling me that half the responses are, "Like Leatherheads? Not interested." They won't even read the synopsis.
A biopic about Darwin sounds a lot like a biopic about Kinsey. Here are the box office receipts for the 2004 film, "Kinsey" from rottentomatoes.com.
http://www.rottentomatoes.com/m/kinsey/numbers.php
So when the film maker says "Darwin," the film distribution companies hear "Kinsey." "Kinsey" got great critical reviews too.