Instead of making complicated new laws, why doesn't Congress simply update existing laws to cover modern technology?
A large percentage of spam promotes outright fraud. If the same messages traveled via US Snail instead of email, the senders would soon face charges of mail fraud. Congress could simply update the definition of mail fraud to include email as well as snail mail.
The law against junk faxes works well. Congress could simply extend the same law to cover unwanted email.
But perhaps that's too simple for elected legislators to understand. They seem to prefer making things complicated.