First off, this script was initially made to benefit individuals in the US, although it also surprisingly works well here in Australia, and I am sure most other locations around the globe would benefit.
This script simply changes the server location that is sending you the video data from your local, potentially crowded server, to one in Canada that amazingly, on average, has a lot fewer clients requesting data. The benefit of this is the Canadian servers have the highest chance to have cached a recent upload that is popular in the US, but without the traffic of the US trying to download this cached info.
A special thanks to Cptmathix, who pointed out that because YouTube uses spf, it may look like the url and page change, but since it is done with dynamic navigation (only parts of webpage change), Tampermonkey will not be triggered (as Tampermonkey only triggers with static navigation). This has since been fixed, by applying Cptmathix's recommendations in v1.3.