This is why I never bought the whole "we should leave more things up to the states to decide" line of argument: as bad as the US Congress is, state legislatures are generally solidly worse; they just don't get as much press. Or maybe this is just a New York thing and other states are different, I don't know.
The constitution doesn't give you a choice. It clearly states that power not explicitly delegated to the federal government must be relegated to the states or the people. You don't like it? Amend the constitution.
Monogamy is relativity new. A few hundred years old.
Your ignorance of history is astounding. Even if you choose not to follow what it teaches, the Bible has taught Monogamy for several thousand years. The Apostle Paul's letters on the subject date back to the first century and the Ten Commandments(Do not commit adultery) to before 1000 BC.
Anyone can make an omelet with eggs. The trick is to make one with none.