Ordinarily, there few laws I can imagine the US Congress passing that are worthwhile. Practically all the stuff that ought be illegal already is, and has been so for hundreds of years. Almost all of the rest is bad law.
That said, the Congress can still pass good laws. Namely, laws repealing other laws, or laws to address or undo problems they have created, or which have been created by the states, or more generally any government level.
Case in point: prisoner rape. Looks like congress is going to address it, though I am not sure how effective the new law will be. Still, it is a start.
Let's look at the problem of imprisonment, from the point of view of the state. Concentrate a bunch of violent men with no effective way to punish them. (How do you punish a life-without-parole prisoner? Slap his wrist?) Deny the men anything constructive whatsoever to do, other than lift weights. Now, apply financial constraint: try to keep them more-or-less from killing each other, at the absolute minimum price in guards' salaries, physical infrastructure, etc.
How to minimize price? You could hire enough guards to keep order physically, but that's expensive -- you would need something on the order of a guard per prisoner. So you want to use the prisoners against each other. How? Get the more physically powerful ones to accept your rule, by allowing them sex slaves -- if they are good.
Of course this "contract" is not explicit. But nonetheless, it is there. And the staff really has no choice, in the sense that if they seriously tried to crack down on rape, they would face the ugly reality of their tiny numbers trying to control tens of violent criminals, each.
The prisons are rape factories. They are also rapist factories.
And lest the heartless reader think, "well they earned it" -- no, they did not. Some of them did, perhaps, if you are the eye-for-eye type. But a good number are there for victimless "crimes" like selling drugs. A good many others are drug entrepreneurs that did something bad (like shooting someone), but consequent to the business they are in. And a lot of others are just dumb kids that made a mistake.
If rape is a just punishment, it should be assigned by judges. Not by happenstance.
And in any case, heartless reader (if I have any), consider this. Rapists, and the raped, in prisons don't stay there. Almost all of them get out. These men are thrown out in the street, many boiling with rage over the way the prison system stood idle, or laughed, at their violation and degradation. These men have been indoctrinated into a hypermasculine rape culture where women are bitches and whores, and where men must literally fight off slavery, to keep other men out of their mouths and anus. If you have listened to gansta rap, you have heard the ugliness. Gansta rap is prisoner culture, leaking out into the mainstream.
The best thing I have read on prison culture, is A Million Jockers, Punks, and Queens by Stephen Donaldson. Donaldson was a kid who got unlucky and made some bad choices early on. He was raped and enslaved, and spent a number of years in prisons observing the culture from the inside. (You can find his story at the SPR site.)
One thing that is clear from an understanding of prison culture: stopping rape will not be easy. I think the valuable part of the new bill, is simply putting funds into studying the problem. What is not valuable, is threatening prisons with loss of federal funds. Does anyone think that federal or state authorities will close a prison because of too much rape? Not likely. Where will the prisoners go? Furthermore, rape must be reported effectively to even show up in statistics. I fear the new bill will create the wrong incentives for prison administrators. The new incentive will be to minimize reported rape; and when you control the reporting, there are two ways to do that.
To really reduce prisoner rape effectively, here are my quick recommendations.
First, allow prisoners to work if they wish, and to contract their labor freely. Then invite businesses into prisons to employ. This gives men something to do other than plot booty-banditry. It also gives the men a means of self respect currently denied them, and hopefully a trade or skill other than crime that they can use when they get out. (I realize this idea is impractical politically because of unions.)
Second, make there be "somewhere worse" to put rapists, in order to have a reasonable threat to hold over prisoners. Divide prisons into two classes: prisons where we do tolerate rape, and prisons where we don't. Men who rape currently locked up in a "don't rape" prison should be assigned to the other class of prison. This, at least, concentrates the rapists together and will serve to hold down rape elsewhere.
Finally, and probably most importantly: surrender the drug war. The creation of a huge class of prisoners for no good reason at all, and exposing them to rape culture, is about the dumbest thing the USA ever did. (I realize this one too is completely impractical politically.)