Bingley,
You generally have well thought responses but I think you're thinking too much by half on this interracial romance issue. There is a well established story line with Glenn & Maggie in the comics and Glens back story in both comic and tv show is that he is very timid and deferential. Their relationship is the longest running of the TWD comic series.
Asian male/white female romances on tv does appear to be rare though I would tangentially point out How I Met Your Mother (though he is Indian), Hawaii 5-0 has Asian/white romances. I think maybe there is not so much because there is not a lot of Asian males on tv in positions that have relationships, rather than a stigma.
For example, look at cinema. I just saw Journey 2 Mysterious Island today and The Rock (Samoan) is married to Kristen Davis from Sex & the city. Then there have been well known movies like: Harold and Kumar (1&2), The Green Hornet, Jackie Chan and Jet Li often have white female romantic leads, Replacement Killers (Chow Yung Fat/Bridget Fonda), Ninja Assassin. Even Brandon Lee before he died had relationships with white females on screen.
I'm not writing so much to be antagonistic. I respect your position, I don't think its entirely accurate (it is somewhat) but I think for a different reason than some sort of subconscious or even poll tested antagonism to that sort of thing.
Written by a guy with a Hawaiian dad and a Dutch mother.