Mexico City to Toronto by Train?

In this video, we learn about the potential plans of joining all of North America together by rail rather than just by air. Europe has had such systems since the 1970s and the nations of North America are looking at upgrading their rail systems to global standards which means that cross the entire continent, north to south and east to west by high speed train could one day be possible. What opportunities are we missing out on by not having this in place already? There are so many possibilities of moving people and freight around the continent in a fast and efficient manner.