You, and Putin, seem to be forgetting a three-way treaty known as the
1994 Budapest Memorandum.There's a three-way treaty known as the
1994 Budapest Memorandum.Essentially, Ukraine agreed to give up all its nuclear weapons to Russia in exchange for safety from a U.S. or Russian invasion. Russia's invasion of Ukraine violates that treaty. And as a signatory to that 1994 Budapest Memorandum, the U.S. has a definite interest in righting Putin's current wrongs.
In the final version of the deal, Russia promised not to attack Ukraine. While the U.S. and the U.K. assured Ukraine they would aid if it was attacked by Russia, that promised aid did not guarantee military support like a NATO country would receive.
In 2009, Russia and the U.S. announced that the assurances in the Budapest Memorandum would continue to remain in effect in the future.
https://www.verifythis.com/article/news/verify/global-conflicts/ukraine-agreed-to-give-up-nukes-in-exchange-for-safety-from-russia-invasion-attack-budapest-memorandum-treaty/536-8748a51f-10ee-47f0-be30-b4088750ee44
Russia promised
specifically NOT to invade Ukraine, and the U.S. promised
specifically to ASSIST Ukraine if the treaty were ever violated. And that's what the U.S. is doing now.