Spending Bitcoin in the US is a pain in the ass because whatever it is that you spend your coins at, it is considered a taxable event. If they make it so that this is no longer the case, then it might actually boost Bitcoin's currency aspect.
That won't happen. Their primary concern is squeezing tax revenue out of us, deterring tax avoidance. They aren't interested in making things less burdensome.
At best, there might be a small annual exemption for gains realized this way, like in
this proposed bill, which caps the exemption at $600. It'll take new legislation to carve out an exemption like that too. I don't think the IRS can just do it.
If the IRS change the status of Bitcoin to being a "legal tender" too, apart from being a tradeable asset, then expect a massive boost in the price.
Legal tender means it must be accepted for payment of debt or taxes. Why would they do that?