Given that the EU has already taken its licks for the ineffective "cookie law" and used that experience to draft the GDPR, I'm inclined to think that length is quite necessary. I'm sure it's possible to express the spirit in a much shorter law, but such a law would be likely to facilitate legitimate activity by simply creating loopholes that severely neuter or even nullify the whole thing (which is one of the common failure modes of US legislation).
Specifically, the EU's teasing out an effective definition of consent is paramount, otherwise the only thing a US privacy law would mean is a few more paragraphs in the bullshit legalese "terms" that nobody reads. Frankly I think Congress should just import the text of the GDPR wholesale and let the courts sort it out. I doubt the outcome could be any worse than what surveillance industry lobbyists end up doing to domestically crafted legislation.