[neilknowsbest]

You're right in principle, but larger interconnections aren't a panacea.

The reality of Uri is that the neighboring regions to the north (SPP) and east (MISO) were on the brink themselves (grid emergency and rolling blackouts in SPP), and the import capacity from their neighboring regions (i.e. the midwest) was constrained; they couldn't import more power from their neighbors. If Texas were part of the Eastern Interconnection AC grid (i.e. connected to SPP and MISO), I think fewer people in Texas would have lost power and more people in Oklahoma. SPP and MISO just didn't have any more power in those areas to ship them.

SPP & MISO have been interconnected with each other forever, they're on the same AC grid. But the capacity between their systems is limited, hence the blackouts in SPP. They just never bothered to build out the capacity because it hasn't made a lot of economic sense. I think that's the best counterfactual example of "what would have happened if Texas didn't have their own grid", and it suggests that the storm still would have been a problem.