Netflix is the main driver of US web traffic, responsible for over a third of broadband data in the country, according to an annual report from Sandvine.
The video-streaming site accounts for 34.9 per cent of downstream traffic during peak hours, while YouTube followed with just over 14 per cent of the market.
Netflix’s closest streaming rival, Amazon Instant Video, only accounted for 2.6 per cent of traffic, although it doubled its share of the market in the last 18 months.
HBO Go came third, claiming one per cent of web traffic - a figure expected to rise following its October announcement that it will offer a standalone subscription service.
On the other side of the coin, BitTorrent downloads through peer-to-peer networks made up just under three per cent of all downloads.
Dave Caputo, president and chief executive of Sandvine, said: "With both Netflix and Amazon Instant Video gaining bandwidth share in North America during 2014, it will be fascinating to see how a standalone HBO Go streaming option will impact networks when it launches in 2015.
"The dynamic streaming video market underscores how important it is that operators around the globe have the business intelligence and big data solutions in place to understand the ever-changing behaviour of their subscribers."
In November 2013, YouTube and Netflix together made up just over half of the US’ web traffic in last year’s report from Sandvine. Netflix accounted for 31.6 per cent of downstream traffic on fixed networks and YouTube was responsible for 18.69 per cent.