Electrical engineers wouldn't build a power line to Texas with a capacity of 5000 MW and then put intertie hardware such as phase shifters or ac-dc-ac converter with capacity of 1000 MW on the end of it. So it is likely that the transmission capacity and intertie capacity are exactly the same!

It's not the capacity of the converter, it's the efficiency of the conversion. There's some loss involved.

They make long distance DC innerconnects, while expensive they are resistant to particular types of problems and can connect to multiple different grids at the same time.

there has been a 3GW DC interconnect between Portland, OR and LA for 5 decades or so. https://en.wikipedia.org/wiki/Pacific_DC_Intertie

That actually isn't true:

https://3dfs.com/articles/wasted-electricity-vs-lost-electri...

Almost 62% of electricity is lost in the grid. AC is the primary reason (matching, vibration, I2R, etc.).

HVDC is WAY better at transmitting power over any appreciable distance.

The article is wildly incorrect: the 62% figure includes the losses during generation e.g. heat lost when burning coal or cooling towers for nuclear.

I recall that losses after generation due to transmission across the electricity grid are typically about 10%.

The Chinese have an amazingly ambitious plan to shift power from one part of the country to another with UHV DC. It has its own challenges, but it is definitely the way to shift massive amounts of power without grid interconnect (and the resulting frequency stability issues). Much lower loss, even with DC-AC converters.

https://spectrum.ieee.org/energy/the-smarter-grid/chinas-amb...

If America built a network of 20GW HVDC interconnects it would be far more significant infrastructure than building some highways.