The problem is that there's no realistic way to fly across the US, supersonically, without massively impacting a substantial fraction of the electorate (who will enthusiastically vote for anyone who will stop the noise).
You can read about the supersonic experiments over Oaklahoma City in the 1960's to learn about the effects of sonic booms, and why people don't like them.
For reference, the Space Shuttle generated annoying sonic booms over west Los Angeles when landing at Edwards Airforce Base. The approach path to Edwards is more than 30 miles from west LA. So, for any supersonic airway, you'd need to set aside a roughly 60-70 mile wide swath of land. That's a lot of people voting to shut down your SST operation (or suing you).
You can read about the supersonic experiments over Oaklahoma City in the 1960's to learn about the effects of sonic booms, and why people don't like them.
For reference, the Space Shuttle generated annoying sonic booms over west Los Angeles when landing at Edwards Airforce Base. The approach path to Edwards is more than 30 miles from west LA. So, for any supersonic airway, you'd need to set aside a roughly 60-70 mile wide swath of land. That's a lot of people voting to shut down your SST operation (or suing you).