There certainly is an inherent reason, which is that Germany and the German economy is dependent on Russian oil and gas as well as fertilizer and a whole host of other natural resources. This inherent reason will initially be felt only economically as factories and industries shut down without the resources need to continue production. In a few months when the temperature starts dropping this inherent reason will be felt in a much more interpersonal way as the German people start freezing to death when they can not afford to heat their homes or find the fuel to do so.
The US do have an interest and they’re dragging/pushing WE into the fire while EE are jumping head first with barely any encouragement.
If anything the EU has proven that the East-West rift cannot be overcome and that they do not have strategic independence.
None of them want to get in an expensive war. And Putin is probably bluffing about using nukes, but who wants to risk it.
There is no inherent reason why Germany cannot singlehandedly support/fund Ukraine's war with a country with an economy 40% Germany's size.
That it cannot is a condemnation of every German government over the past 30 years. (That NATO's European members cannot do so either, and that the US is providing the bulk of the Ukraine aid, is correspondingly a condemnation of every member government over the past 30 years, although the newer members get a pass because they are a) small, b) poor, and c) actually meet the NATO 2%-of-GDP guideline.)