Re: highways, thank you for pointing that out. I've fixed the article by s/interstate highway system/public works program/ with link to the details. Btw, FDR spent over $4B on highways, roads, and streets, a considerable sum in those days.
Re: You can't aspire using the impossible." Naysayers like you are why we may hever have this.
How do you know it's not going to be 2 hours? Or 1 hour?
The evidence you presented requires a straight connection between the two cities. That's not going to happen, for reasons I presented and for which you yourself agreed.
If it happens it will be via regional hubs, say via Chicago and Denver. Even non-stop (with no additional acceleration and deceleration) that non-GC route will add more time. Plus there's the 10 minutes or so for acceleration/deceleration to 600mpn.
If you pigeonhole me as a naysayer then may I pigeonhole you as one of those Project Plowshare advocates who wanted to use nukes to make harbors and canals, and fracture the ground for oil production? Or as a modern Lyle Lanley?
I'm asking you to use realistic numbers which make you seem well-informed, not numbers that are easily dismissed as overly optimistic, if not ridiculous.
Just like in Marge vs. the Monorail, US infrastructure is horribly under-maintained. https://www.infrastructurereportcard.org/ for example. That sort of Federal involvement in local projects is more in line with FDR's Great Depression actions than Eisenhower's interstate system.