I believe the easiest way to create a high speed intercontinental railway would be utilizing the medians of existing interstate highways.
Simple
You build the support pillars in the middle of the medians of existing interstate highways. The high speed rail tracks would be fifty or so feet above the medians, high enough to clear both the roadways and overpasses.
The Van Wyck Expressway in NYC utilizes this method.
Stations could be placed at various points along the system on sidings that can merge onto the main line.
Utilizing existing interstate right of ways can cut down on eminent domain issues and could lead to at least 85% of the system being constructed without having to do much.