What do you mean by "would" say that? You can say that, thanks to our First Amendment.
The fundamental problem is that there just aren't enough people who are prepared to sever the US. If I wanted to grow a secessionist movement, I would try to find a single uncompromisable issue to divide people into two groups. Slavery was that kind of issue. I don't see such an issue out there right now.
I guess you must be a socialist.