> * ... driving licence ... company laws ... *

Except (AFAIK) none of these has ever resulted in 50% of someones wealth/future-wealth/ip being "awarded" to someone else.

> Also, other than legalizing no-fault divorce and expanding marriage to same-sex couples, what are the changes that states could make which are so scary to you?

Beside legislative branch, judiciary also gets to set precedents as it go.

> Sharing wealth 50/50 in the case of divorce is not some new thing.

It was new when first time it happened. Since it could not have been in marriage contract or constitution. It must have been made up by courts.