This is actually not true. If you look at the Wikipedia article on supercomputers you'll find that there is a special network for Bitcoin because it can only do

This is actually not true. If you look at the Wikipedia article on supercomputers you'll find that there is a special network for Bitcoin because it can only do sha256x2. Specialized mining hardware is in the exahashes range whereas even the best general purpose are terahashes at best and even that is a stretch. Plus the attack has to be sustained, you can't just do it for a few seconds or minutes and disrupt much.