Tallcal, this is not a wall that has has been knocked down that was dividing people. Gay marriage is not about marriage, it's about yet another special interest group forcing their wishes upon the majority.
In the United States and other similar cultures, marriage has become a social institution, but it is first and foremost, and is still very much grounded in, the institution of religion. A Civil Union would give same-sex couples all of the legal rights that a marriage would. In fact, a marriage presumes and mandates the legality of a civil union by the issuance of a marriage license, which is a civil document. But a Civil Union without the attachment of the word "marriage" to it is unacceptable to gays and lesbians, even though a Civil Union gives them precisely what they are asking for. In other words, they don't really want what they are proclaiming, which is the same legal rights as any other married couple, but rather to force their will onto the religious connotations to redefine marriage as they see fit.
They aren't asking for equal rights in marriage, they're asking for special rights. Because most of the world's religions, and the dominant religions of America, all denounce homosexuality, gays and lesbians are just as much, if not more, concerned with "winning" against religious attitudes as they are about equal rights under a Civil Union. Civil Union wasn't good enough, they wanted to go after the Marriage word.
In Europe and other countries, same sex marriage isn't as widely and enthusiastically embraced as you would like to believe. The Netherlands, Belgium, Norway and Spain are the only European countries to offer marriage to same sex couples. That's it. Four of 'em. Outside of Europe there are but two, Canada and South Africa. And Canada and Spain are the only two countries where same sex marriages have exactly the same legalities as traditional marriages, with there being no differentiation of marriage types. The other countries named above, as well as about 22 other countries, have varying legal status within the context of marriage, or within the registered partnerships, civil partnerships, domestic partnerships and civil unions.
There are a handful of other countries (twenty one of them including the US) where some time of legal partnership (most are highly limited, some not so much) is allowed in some parts of the country, like here in the States, where we have 9 states (including D.C.) that allow civil unions and the variations: California, Hawaii, New Jersey, Vermont, Connecticut, Maine, Washington, Oregon, and Washington, D.C.
This is a hot topic world-wide, so don't for a second think that Americans are behind the times, or worse, that Californians are the "enlightened ones".
Funny thing is, the notion of same-sex marriage in gay and lesbian circles is actually the conservative bent of things. The more liberals of the bunch want "marriage" and all the legal rights thereof to encompass "couples" of three or more intimate, lifetime partners. And apparently, there's a whole bunch of those out there.
Wooooo. There ya go. Now yer talkin' slippery slope type stuff. Where does it end? I've got a friend who has been a part of just such a lifetime threesome. (OK, so he's not that close of a friend, just a friend.) But, if one or two of them die, the survivor(s) currently don't have a legal leg to stand on, with the exception of their Wills. What do they do? I dunno. They don't get married, tho.
Incidentally, all three of them wear a wedding band. It's all very weird.