comScore has just released their December 2011 U.S. Online Video Rankings, and it comes as no surprise that Google sites, led primarily by YouTube, took the crown.

U.S. internet denizens watched a lot of online video in December – 23.2 hours per viewer. Throughout the entire month, a total of 182 million users watched a whopping 43.5 billion videos.

As far as unique viewers go, Google sites led the charge nearly tripling up the next closest competitor, VEVO. Google claimed 157.2 million unique viewers who watched 21.9 billion videos in December. Google sites also held high viewer engagement with about 7.9 hours of watching per user.

Hulu, who finished in 8th place in terms of unique viewers with 31.2 million, also had impressive engagement. Hulu users spent a little over 3 hours on average watching videos on the site.

Americans also viewed a total of 7.2 billion ads last month, spanning 3 billion minutes. These video ads accounted for 14.1% of all the online videos viewed in the month of December. Hulu was tops in terms of video ad impressions with around 1.5 billion. They were closely followed by adapt.tv with 1.1 billion and Tremor Video with 900 million.

Finally, VEVO is still the top YouTube partner with 53.5 million viewers. They also had the highest engagement numbers with 66.9 minutes per viewer over the course of the month.

A couple of bonus figures: 85.3% of the entire U.S. internet community viewed online videos. The length of those online videos averaged out to 5.8 minutes, and the average ad was only 24 seconds long.