Ethereums only actual real use case thus far has been issuing ICO's. Billions worth of ICO tokens have been deployed by Ethereum's smart contracts.
Now imagine what would happen if governments really banned ICO's... I don't see how Ethereum wouldn't suffer from a massive crash.
Bitcoin would probably be fine, except the same idiots as always that sell at any headlines containing ban+crypto/bitcoin would also dump, but it would quickly recover. Ethereum... not so much.
Let's hope this was it for Bitcoin and we are going back to $5000 now, double bottomed and it's going up. Hopefully not heads and shoulders formation with further drop, that would suck.
Ethereum has lot of more use cases but the ICO Scene use it cause its not so difficult to program an ERC20-Token and an smart contract to work with the blockchain. But others have done ICOS with NEO and NEM XEM. The use cases of ethereum are widley spread.