(And sometimes a system being extremely stable just means it's brittle, not strong)
The design of electrical power grids is such that their control systems are by their very nature suppose to keep frequency and voltage within tolerances no matter the unpredictability of the grid. This is the definition of stability and resiliency that you're talking about. And the design takes into consideration failures of any device on the grid.
That being said, even being a minor power grid, it isn't actually isolated. Its just not subject to FERC regulations. But for the most part, its own regulations are similar to that of what other grid operators are doing, because it makes sense to do for grid stability reasons.
"The Texas Interconnection is tied to the Eastern Interconnection with two DC ties, and has a DC tie and a VFT to non-NERC systems in Mexico. There is one AC tie switch in Dayton, Texas that has been used only one time in its history (after Hurricane Ike).
On October 13, 2009, the Tres Amigas SuperStation was announced to connect the Eastern, Western and Texas Interconnections via three 5 GW superconductor links.[2] As of 2017, the project was reduced in scope and only related infrastructure was constructed for nearby wind projects connecting to the Western Interconnection."
There is indeed risk for cascading failure but it is very rare (how long have the US grids been interconnected vs. how many times has there been a massive, multi-state blackout?) and with EU countries higher attention to infrastructure maintenance the risk is even less.