Okay let me rephrase it then, it will likely come out NON supportive of EXISTING crypto's. Remember what I said, "Government loathes what it can't control" If the US government creates it's own crypto, it will likely put regulations in place to limit other crypto currencies to encourage adoption. They will limit other currencies because of money laundering, illicit goods, tax evasion, and power requirements (environment)
What do you think will happen to the value of bitcoin/eth if you can't exchange it for greenbacks? I'm personally fine with a gov't based, regulated, and BACKED crypto PROVIDED each transaction is traceable, and has low power requirements not based on POW algorithms.
At the very least if energy concerns aren't an issue, crypto will be put under such heavy regulations that only banking institutions with a clear trail of money and exchanges will be able to handle it so it can be tracked and taxed appropriately. Thus negating one of key benefits of crypto for many. (Anti-govt regulation) Coinbase and the like would likely not get gov't approval as a banking institution. The regulations they put into law about transactions make it almost impossible to enforce with so many small exchanges.