The Iranian nuclear red line is outdated in this era of globalization, and this new agreement effectively just, uh, nukes it entirely. The technological difference between enriching uranium to an allowable medical isotope level of 20 percent and enriching uranium to weapons-grade 90 percent is negligible. Moreover, when a nuclear Russia is already building Iran's facilities -- picking up the ball dropped by a nuclear China in the early '90s -- and Iranian foe Saudi Arabia can have a nuclear bomb shipped from Pakistan within mere days, the debate over Iranian's capacity for nuclear-grade military power is moot.
Pragmatically speaking, two things can deter Iran from using military-grade nuclear capabilities.
First, the international community would have to stop debating whether Iran is in compliance with nuclear laws governing the entire globe and instead have the guts to pass laws that are framed in such a way that they pertain directly to Iran. If that country indeed poses a unique risk, then acknowledge that through law rather than declaring victory over the vaporization of a red line that is unenforceable anyway. That's not a victory of substance -- it's simply a cop-out.
Bailing on the babysitting of Iran wouldn't necessarily be a bad move for America. And if the new agreement is simply a face-saving move for Obama to do exactly that (which I suspect it might be), it's hard to take issue with it.
The Russians seem keen on taking over the babysitting job, given Russian President Vladimir Putin's masochistic affinity for mentoring "challenging" world leaders in his own backyard. America has already punted another problem child into Russia's care, washing its hands of Syria. There was a time when the Middle East and its energy reserves were of prime strategic importance to America, but with North American energy self-sufficiency reachable within the next few years, it's becoming harder to justify this ongoing geopolitical migraine and the allocation of resources that it requires.
Second, the threat of regional mutually assured self-destruction as a nuclear deterrent for Iran can't be undervalued. Saudi Arabia and Israel are both making clear their willingness to retaliate against any act of Iranian nuclear aggression in the region.
North America's primary strategic focus heading into the future -- on economic, military, and diplomatic fronts -- must be China. This applies to all of its activity around the world, particularly in emerging markets. Outsourcing the policing of the Middle East to state actors with greater stakes in the region makes sense.