In Malawi at least, the idea that American evangelicals are the major force behind the anti-gay agenda is, I think, not an easily supportable hypothesis.
Evangelicals are turning into the the Western left's "TEH JOOS!!!"
First they came for the racists, and I didn't speak out because I wasn't a racist.
Then they came for the homophobes, and I didn't speak out because I wasn't a homophobe.
Then they came for the pro-lifers, and I didn't speak out because I wasn't pro-life.
Then they came for the marijuana opponents, and I didn't speak out because I wasn't Adam C. FitzGerald.
Then they came for me, and there was nobody left to speak for me.