To M-Maven: ask any accountant about taxes, marriage, etc. to see how much marital status is tied in to civil law. One of the many reasons there is such agitation for recognition of alternative marriage.
And Haifagirl, there is such distaste for polygamy in the US – for good reason, considering the horrible farce of marriage that passed for polygamy here – that agitating for polygamy would be a major, major chilul Hashem. And not too many people other than Sefardim,, maybe, have a mesora of how it should be done properly.
And IIRC it didn’t work out too well as long ago as 1000 years ago in Ashkenazic circles. I can’t imagine how, with yeridas hadoros, we could make a better go of it in the 5770s.
(Remind me again, why am I taking this seriously?!?)