| Its not primarily a "supervise the ex-Soviet union's nuclear materials treaty." We've had agreements about that before, and we could have agreements about that without directly have this specific arms control treaty, or any tighter limit on strategic weapons. Also the actual monitoring involves a lot more ongoing agreement and working together than just some signature on a paper followed by ratification.|
.it would have made the world and the US a much more unsafe place
That's false in at least two ways. The treaty itself won't make things much safer, and even if it somehow would have the lack of it wouldn't make things more dangerous it would leave things the way they where before/without the treaty. Even if the status quo is "dangerous", it still wouldn't be "more dangerous", or to use your words "much more unsafe".