I think such a law banning the bundling of cable networks could face constitutional challenges on First Amendment grounds.
How does the 1st amendment fit into this?
Obviously it not the religion clauses, nor related to petitioning the government for redress.
I don't see a press issue, since it's not controlling the creation/publication of material. A law requiring bundling I could see bumping against this, but not one limiting/prohibiting the practice.
And it's surely not a speech issue, since it's not controlling the content of any "channel" nor it programs. If anything it could be a plus in this case since you are not required to support programming you disagree with any more.
Note too, that the speech at issue in the 1st amendment is political, as in complaining about the government. There are plenty of restrictions about what/how other speech can take place. From slander and inciting violence to causing panic and reporting false crimes.