State-level data & multi-state holding companies

The demand would be based on the resident household and local industry and other institutions within the region. Supply (and distribution for power) would be establishment based. Where are the establishments? Where are the employees. There are many companies with offices and branches all over the US - but employment, income and output is workplace based.

Thanks. So, for “power generation and supply” would electricity generated by an Oregon-owned utility at a (for example) Washington-based hydroelectric dam would be shown as Washington in-state supply, not Oregon in-state supply?

Correct, the production value of electricity generated by that dam in Washington is an import if used in Oregon. The imputed distribution markup occurs wherever the administration and maintenance employment is based for the distribution. Power generation and distribution gets messy.