Anyhow the American answer (under the evangelical, popular model) worked as long as the significant We The People bothered to be godly. However, they carried governmental authority over marriage by inertia from the English monarchy, which in turn got it from the Anglican church which earlier had been, of course, the Catholic church, which in turn had been a piece of the original church.
Lose the godliness and the result is as tragic as the falls of ancient Israel. The structure is misused and the results hideous.
A huge part of the reason why we are in this mess now is that many have been conditioned to believe the state defines marriage. The faith groups that have accepted ‘gay marriage’ won’t even marry their gay members unless the state they happen to be in does too. The state decides these things for them, I guess.
In the modern era, the state can only get its definition by whatever judges, pols, or the voting majority currently think marriage should be at any one time. And that’s it. Like you say, this was always a danger.
Freegards