The US government / political class is risking a great deal for very little benefit.
Amazon, Paypal, Facebook, Twitter and Google* are US companies which contribute massive amounts to the US economy. These companies are all global brands, and as such their success relies upon non-US citizens, 95% of the world's population, feeling able to trust them with their data and custom. If due to the US government's actions we start moving to non-US based alternatives the US economy will suffer badly in the long run.
This huge risk needs to be balanced against what they hope to achieve - the best outcome for the US govt would be that they get their hands on Julian Assange, prosecute him successfully and jail him for a very long time as a deterrent to others. However, anyone following this story knows that that's very unlikely. Extradition from the UK or Sweden to the US will prove almost impossible, and even if he did end up in the US, expert US legal opinion is that it's unlikely that he could actually be prosecuted for anything. Beyond that, the 'deterrent' aspect would also fail utterly - Assange would become a martyr and 100 Wikileaks clones would appear in its place.
For its own self-interest the US badly needs to take a step back, accept that Wikileaks has a right to exist and tighten up its own internal security to try to prevent leaks in the future. After all, we know that if Wikileaks' current target was Iran, China, Russia or many other countries, the US govt would be applauding them rather than trying to shut them down.
*It's reported and seems almost certain that Facebook and Google have received subpoenas along with Twitter. Apple's actions in removing a Wikileaks app probably have more to do with their own procedures than any political pressure. The most likely to suffer is Paypal - I am very angry that a US Republican senator can control who I can and can't donate to.