He's not. He's acting in the US's genuine national security interests.

Russia is not a threat to the US.
The ideology of international socialism (communism) was a threat to the US - hence US support for free Europe in The Cold War.

Russia may be a threat to Europe, but that is traditional European rivalries which the US has traditionally avoided getting involved with.

Germany is not a threat to the US.
The ideology of national socialism (Nazism) was a threat to the US - hence US support for free Europe in WWII.

The Ukraine - Russia war pushed Russia closer to China and Iran. That is BAD for the US.

The biggest current threat to US national security and to humanity as a whole is the ideology of globalist woke socialism - the Woke Mind Virus.

Europe is heavily infected with The Woke Mind Virus.

Russia is not.

It may be in the US's interests to allow or even encourage Russia to conquer Europe to defeat The Woke Mind Virus.