As I said, there is a huge difference between making others conform to our laws here, and going into their country and changing theirs. As far as people coming here, they should be made aware of our laws and respect them. That might mean that the man would continue to take care of any women or children that he has "married," without sleeping with them, or giving them some time to get it figured out or whatever. I see it no differently than how we would treat someone coming to the U.S. with slaves. That slave would need to be able to care for him or herself, or be cared for in the interim. However, the slave owner would not be able to "own" the slave anymore, as this is illegal here, and as well it should be.
Again, adultery whether from the concordance, or the dictionary has one definition. The meaning of the word does not change depending on whether or not it is a male or female. The New Testament, for the first time in scripture shows that a man can commit adultery against a woman.
As for the comparisons to God's kingdom to slavery, here is one of many...
Matt 24:45-51
45 "Who then is the faithful and wise servant, whom the master has put in charge of the servants in his household to give them their food at the proper time? 46 It will be good for that servant whose master finds him doing so when he returns. 47 I tell you the truth, he will put him in charge of all his possessions. 48 But suppose that servant is wicked and says to himself, 'My master is staying away a long time,' 49 and he then begins to beat his fellow servants and to eat and drink with drunkards. 50 The master of that servant will come on a day when he does not expect him and at an hour he is not aware of. 51 He will cut him to pieces and assign him a place with the hypocrites, where there will be weeping and gnashing of teeth.
NIV
As to the comment about monogamy being a modern day ideal, you are wrong. Monogamy was started and created by God almighty, and it is the way that He originally set up marriage. In fact it is how He defined it.
A good question was posed. If a polyandrous "family," moved to the U. S. should they be made to conform to our laws?
The 2 become one flesh issue: Regardless of whether or not one flesh means one person or one "family" the fact of the matter is that the word two, is still two. He does not say the 3. or 4, or even, they become one family. He very specifically says ,"Two." Also, according to my concordance, there is nothing to suggest that the word flesh means family anyway.
I see this as those believing that polygamy is still ok, believe that Christ's coming did nothing to bring any restoration from the curse.