USA wanted to limit spread of nuclear weapons, and talked Ukraine into giving all these weapons away, and received security assurances from USA and Russia instead.
This was the sum of the Budapest Memorandums.
Clearly, USA have failed providing the security guaranteed in the 1994 memorandum.
US should therefore, to honor their agreement, return the nuclear weapons to Ukraine, so they can defend themselves against Russia.
This should be done with a high profile handover of a red button in Kiev, so Moscow and Putin is alerted to the transfer.
There will be no need to use any of these weapons. Just displaying the capability will make Ukraine safe against Russian aggression.