What this means for the US
Irrespective of whether the purge weakens or strengthens Prince Mohammad, the net winner has been President Trump. In one fell swoop, much of the funding for his liberal opponents within the US has been threatened, given the deep penetration of Saudi resources in the US media and social media. Should the kingdom decide for example to confiscate Prince Al Waleed Bin Talals shares in Twitter and Facebook, this would mean direct influence on their censorship policies and content, available for Trump to apply on demand and outside the ambit of US law. More importantly, the Saudis can no longer claim that Prince Talal is an independent centre of power not prone to their influence. Similarly the consolidation of the Sunni arc, will drastically increase Iran's threat perception, forcing it into ever more aggressive actions such as missile testing, which though not covered under the nuclear deal (such as missile testing), certainly give opponents of the deal much fodder. The argument here is why does Iran need missiles that are militarily useless without nuclear warheads? This strategy of permanent tension vis-a-vis Iran, may very well end up forcing Iran into a series of actions which may lead the west to conclude the nuclear deal is simply not worth it. This dovetails neatly into the Saudi quest for geopolitical prominence, Israel's quest to be free of what is possibly its most potent enemy to date, and Trump's assertions that the Iran deal is fundamentally bad.