Why didn't the US just complement Russia's security demands to avoid the invasion of Ukraine?

Shortly before the invasion of Ukraine happened, Russia sent its security demands to the USA. The USA rejected these proposals, and many people say they were unrealistic. However after reading the document, I can't see why exactly. Most of the articles work both ways and include mutual security and tolerance, and I think the only questionable part was Article 4:

The United States of America shall undertake to prevent further
eastward expansion of the North Atlantic Treaty Organization and deny
accession to the Alliance to the States of the former Union of Soviet
Socialist Republics.

The United States of America shall not establish military bases in the
territory of the States of the former Union of Soviet Socialist
Republics that are not members of the North Atlantic Treaty
Organization, use their infrastructure for any military activities or
develop bilateral military cooperation with them.

However, it's nowhere near what I thought it could be. Russia didn't ask to exclude any of the current NATO members or stop accepting any new countries. Russia essentially asked to ban not-yet-joined ex-USSR countries, which I find quite reasonable for maintaining the so-called buffer zone. I understand that in its current form it poses security risks for those states as well, but the US could complement the treaty with another article which guarantees security of these countries from the Russian side.

If the US had signed such a document, Russia would have to violate another international agreement to invade, let alone that Russia would lose another excuse for invading.

Wasn't it a fair price to avoid the armed conflict?