The only copper you find 'just lying around' is copper being used for power or data transmission.
I assume you've never found a pre-1982 penny.
Part of what made the Boston Tea Party as powerful as it was is the destruction of property-- the valuable tea. The crux of the RIAA's problems is that mp3s have no inherent value. Sure, perhaps nothing has inherent value, but at least with tea there is the issue of a limit on supply. There is a replacement cost. Were such a thing possible, we could dump all of the mp3s we wanted into the ocean and the RIAA wouldn't bat an eye because those mp3s are limitlessly reproduceable at, functionally, zero cost.
Digitization and the move away from physical media, while often increasing the availability of niche products, has largely been a systematic approach to disempowering the consumer. Your mp3 has no resale value. You cannot always legally transfer your license to another person, even for free. You cannot undertake fair use because to do so would be to violate the DMCA. Scarcity [of the mp3 itself], storage, and manufacturing costs [not music/movie production costs] no longer contribute to pricing and the medium itself no longer retains any value.
Boycotts become less effective (though, perhaps slightly) because retailers don't have to worry about storage costs as inventory piles up or ordering more or less mp3s. The cost of storing a given mp3 is fixed and minimal, no matter how many people purchase it. The retailer doesn't incur more costs until it must use bandwidth to provide it to you.
I realize that this response ignores the spirit of your allusion to the Boston Tea Party as a spirited and dramatic protest, but I feel like the failings of the comparison are worth exploring because they illuminate some of the issues at play.
As far as the philosophy of taxation is concerned, I have doubts that this applies. When you purchase a song from iTunes or in any way obtain a legitimate, legal copy of a copyrighted work, you have not purchased a good or a product. You have purchased a license allowing you to use a copy and that license is basically a contract. Between the two, this more strongly resembles a service, not the tangible goods for which a sales tax is designed. If intellectual property is going to be taxed just like tangible property, then I want the right to do whatever I want with it the same way I can do with tangible property. I have the funny feeling that copyright-related interest groups wouldn't like that very much.
The problem with this line of argument is that you already pay sales tax when you purchase a license to use software (delivered on physical media) and the copyright system has continued to function, in its own quixotic way.
That aside, I have no qualms with your argument that there should be a real need for an increase in taxation.
If you look at this from the point of view of NY State, however, the real question is more likely to be "why are the sales of these downloads not taxed like the sales of everything else?" or "why are we forgoing this revenue stream that is entirely consistent with our philosophy of taxation simply because our outdated tax codes do not account for new media?" From that perspective, one could even argue that the fact that such downloads have gone so long without being taxed is a product of mismanagement.
As for the distinction between "use tax" and "sales tax," I see what you're saying: what you call it has no real effect on your wallet. But the difference does have a practical implication insofar as changes regarding sales taxes are about changing your legal obligations (creating a new tax on iTunes downloads) but, at this point, changes regarding use taxes are more likely to be about enforcing your pre-existing obligations (forcing Amazon to collect NY taxes because they darn well know you're not likely to actually pay them even though you're already legally obligated to). Implicit in this is the fact that for a state to charge use tax, the item in question must first be subject to sales tax.
Certainly, this particular distinction will make the proposal no more desirable to you. In fact, gleaning what one might about your economic politics from the posts above, the distinction would probably make the change LESS desirable: because this is about sales tax, it is about changing your legal responsibilities rather than simply holding you to those that already exist.
My problem lies in reconciling my gross habits with my net income. -- Errol Flynn Any man who has $10,000 left when he dies is a failure. -- Errol Flynn