What’s stopping more electricity being generated in the US? It’s both financial and political, but private business could step up here?

Permitting reform is currently working its way through congress, for what it's worth.

It's federal permitting, local "NIMBY" veto control over everything, state environmental laws, tariffs on solar equipment, and out of control costs on infrastructure in the US (a combination of corruption, overpowered unions, and regulations).

Like many problems in the US, the causes are many and diffused across different layers of government, different departments, making it very difficult to solve.

regulatory capture by coal and gas companies