There's a few problems with that.
1.) It wouldn't be an enforceable law to have everyone report all contact information to the US government. What's the government going to do if someone generates an address and send bitcoins to it? They could look up who sent the bitcoins there, but they don't know where they went and they don't know if it was intentional on the part of the sender. Are they really going to track down every unreported .1 bitcoins sent somewhere by somebody?
2.) The US government has no control over what foreigners do. Are they going to ban all international transactions of bitcoins? Not possible.
3.) That's a huge violation of privacy without a warrant.
4.) What are they going to do about off-chain transactions?
You say that people could withhold their money with fiat, which is true, but you could never do it as easily and thoroughly as you can with bitcoins.
I just don't see it as being as easy as you make it out to be.
I disagree with #1.. Surely you've heard in the news about the feds tapping all these corporate databases (Apple, Microsoft, Verizon, etc.) for their customer information. As it stands now there's no law forcing companies to proactively supply info to the feds, but I can't imagine a reason they couldn't legislate something like that. They already have tons of mandatory reporting (accounting, payroll, etc.) so this would just be one more thing on the list. Once this reporting requirement is in place, it will be easy to have a cross-reference database that correlates addresses with name/address info. For non-tech-savvy people (the majority), they wouldn't be cautious enough to anonymize their addresses when making purchases, and they would expose their accounts in their wallets.
for #2, I was only referring to technically-challenged US citizens and how they will be subject to US income tax
for #3, Prism
for #4, this falls into the same category as well-anonymized transactions, requiring knowledge the average person isn't privy to and thus couldn't capitalize upon.
For comparison look at the supposed "Bitcoin Banned In Thailand" reports. One part of a regulatory entity made a single mention of Bitcoin, and attention seeking bloggers sensationalize the comment.
Definitely this court case was more sensationalist than definitive, but it's the psychological impact this kind of case has that makes it transitional in the sense that it's a step in the direction of becoming a bona fide currency. I believe the only thing that distinguishes Bitcoins from a real currency, is its taxability. If and when (and how?) they start to tax your bitcoins, that will be the official day it becomes a real currency.