There are a few reasons why US internet speeds have stagnated, and neither of them have anything to do with the NSA, if the NSA is doing anything to anyone it's doing it to everyone.
The first reason is geographic, the US is a very large country with a very dispersed population. This makes delivering high speed internet to the majority of the population a very large infrastructure project. Most of the countries with much better internet are much smaller and more densely populated or have a very different population distribution pattern.
The second major reason is unlimited data caps. Under unlimited schemes every economic incentive is to oversubscribe and under invest. You don't make any money by increasing capacity, just by increasing customers. I know this is an unpopular opinion in the US, but it's reality. If you want your ISP to be motivated to get you speeds, pay for use.
In the absence of private investment to build this kind of infrastructure you're only real option is public money, this is happening a little bit at the local level, but debt aside major infrastructure projects with huge costs and timelines are political poison at the state and federal level. Rolling out a network that could deliver what South Korea has for instance would cost several trillion dollars(FTTH was projected to cost about 50 billion to deliver to 93% of Australian and well over half the Australian population lives in 5 capital cities with most of the rest in cities a couple hours drive from those same cities). It's just not going to happen in the current political climate.