There was the civil war where the seceding states drafted their own messy Confederate Constitution, and developed their own fiat money. They tried bolstering it with Confederate Cotton Loan Bonds sold to foreign investors, but northern victories, the naval blockades and targeted burning of cotton warehousing really screwed their plans.

No Constitutional Convention has ever been called by the states though. There have been some weak proposals that got passed over to amend the 2nd amendment and stuff but nothing else.