The CFTC is debating whether or not to put bitcoin under their supervisory remit, which in essence will place all exchanges under the scrutiny and regulation of the CFTC.
But that doesn't prevent exchanges from operating. They just will have to jump through regulatory hoops, which admittedly adds cost.
In the US, what I hope to see is that there is a safe and perhaps regulated way for people to get into bitcoins. I don't mind this type of regulation because it will make people feel like bitcoin is safe because the government is regulating it.
The key goal for bitcoin promoters like myself is to get people into bitcoin. If that means going through regulatory hoops, then fine...because even as you pointed out...
Won't affect P to P usage obviously
...once people are in bitcoin, it's game over for any chance at effective regulation.
Also, keep in mind that the US isn't the only country in the world, and that others have taken a different approach to bitcoin, such as Germany and even China.