Polygamy became a non issue when no fault divorce (which was the big enchilada and which makes everything else other than pedophilia irrelevant) if there is no penalty for a guilty party betraying their spouse then you pretty much were allowing anything at all anyhow.
God spends a lot more time condemning divorce than He does polygamy because divorce hurts more people than polygamy.
On a large scale, polygamy leads to social instability because there aren't enough women to go around, and the men on the outside looking in are, obviously, very unhappy. They won't work hard, they are depressed (even suicidal), with increased substance abuse and crime. Polygamy is not consistent with social harmony.
This being the case, it will be coming back in this country, of course.