That's ridiculous, and hopefully nothing like that passes.. it seems overly draconian, and would cause a need to counter-adjust in a lot of other areas..
Not just ridiculous, but demonstrably impossible. The government would have to track the value of all assets. Wyden has a lot of good things to say, but he is embarrassing himself here.
It's perfectly possible. I mean... I didn't know that's not the case in USA, but in other countries that's exactly how it works. You are taxed annually for any assets value above a certain exempt limit (ie: around the first million total net worth in the case of Spain).
It is you who need to declare values and pay your taxes. Only in the case you get audited it is the tax agency who tracks the value of your assets and determines if you did it right.... and if you don't, you are fucked *big* time.
Also for most assets it is automatically calculated and compared to your declaration. If a significant mismatch is detected, you get audited.
That's basically how it works.
And that's the reason wealthy people diversifies into exempt investments, move assets into corporates.... and lots of other financial schemes to (legally) avoid it.