Well yeah, you have me reading up on it now, and it does seem like the US has an awful lot of bad legislation.
But consumers and sellers alike still have to abide by the UCC (Uniform Commercial Code) which is currently ratified as state law everywhere in the US except Louisiana.
It looks to me like the two paragraphs that would make it illegal for Steam to take your games away, or write a TOS agreement that enables them to, are right on top of eachother, paragraph 2-301, and paragraph 2-302:
§ 2-301. General Obligations of Parties.
The obligation of the seller is to transfer and deliver and that of the buyer is to accept and pay in accordance with the contract.
§ 2-302. Unconscionable contract or Term.
(1) If the court as a matter of law finds the contract or any term of the contract to have been unconscionable at the time it was made the court may refuse to enforce the contract, or it may enforce the remainder of the contract without the unconscionable term, or it may so limit the application of any unconscionable term as to avoid any unconscionable result.
(2) If it is claimed or appears to the court that the contract or any term thereof may be unconscionable the parties shall be afforded a reasonable opportunity to present evidence as to its commercial setting, purpose, and effect to aid the court in making the determination.
In other words, 2-301 specifically states that the obligation of the buyer is to pay, and the obligation of the seller is to provide.
And if you write up a TOS agreement in bad faith, or one that makes unreasonable demands of the signee, it's void.
Here's the code itself: