Things like the Real ID Act seem to be as close as we can get without constitutional changes. Something like the above could potentially be implemented like that, but still would not be as widespread as an SSN.
Prior Supreme Court cases have ruled that the Federal government cannot coerce the States, e.g. via taxation or regulatory authority, to do something for the Federal government that the Federal government is prohibited from doing itself. Without the voluntary compliance of the States, which is like herding cats, with respect to creating a national identity database, the net effect of Real ID will basically be more standardized State IDs.
You seem very sure of these Supreme Court decisions that appear to have slipped past the rest of us. Not saying you are wrong, with the firehose of info these days it's easy to miss things, even really important things.
There isn't one court case that informs the boundaries of the Federal government and ID, and how the government may facilitate the linking of an existing identity token to their database, it is diffused across many. The policy and regulatory practice in the Federal government threads a convoluted path through this precedent, with myriad loopholes and workarounds, and exploiting gray areas that have not been adjudicated. I've worked in this environment, which is the only reason I know about it. Every time they create a database on US citizens, they must articulate the title authority that both allows that database to exist and to be used (use and existence are, somewhat dubiously, deemed separate authorities which notionally allows them to collect data if they don't look at it -- this reasoning is not well-tested).
In practice, the US government outsources identity stuff to companies like Lexis-Nexis, which rely on duck-typing to determine identity since this doesn't require the person being identified to carry a token. Just about everyone carries an ensemble of tokens that are sufficient for identity purposes if you have fewer database building prohibitions than the US government.
It went into effect in 2014. You are probably confusing Phase 4 requirements (the requirement for Real ID for commercial air travel being the main one) with the act as a whole. Real ID are issued, and are required for a variety of purposes.
> Prior Supreme Court cases have ruled that the Federal government cannot coerce the States, e.g. via taxation or regulatory authority, to do something for the Federal government that the Federal government is prohibited from doing itself.
Which would be relevant if cases had also established that the federal government cannot issue photo ID cards that the Federal government required for functions subject to federal regulation under the Constitution.
But no such ruling has been made, and the federal government issues a variety of IDs (passports, permanent resident ID, military ID), and mandates their use (allowing, in some cases—like commercial air travel—the use of an acceptable alternative) for a variety of purposes.