Yes - but IMO, as soon as you've shed any significant amount of load, you've failed.

If just 10% of a nationwide grid is down, there's a good chance the phone network won't work, internet will be down, trains won't run, credit card/payment systems won't work, etc. All those things have primary and backup systems, but somewhere in the chain of dependencies there will be both a primary and backup that have been shed, and the system designers thought "these two data centers are 500 miles apart, so won't fail together".