You could have fooled me.
Germany (and Europe as a whole) is paying for this in the form of LNG imports from the US and the UAE.
https://www.wsj.com/articles/fresh-leads-point-to-poland-as-...
In any case, why would the US have to pay? It's not like anyone else has the power to extract a payment. In fact, for now the US is the country getting paid in the form of increased natural gas exports.
The US will have to pay twofolds, financially and morally. As Larry Johnson said: 'What has happened in Ukraine in the last 19 months — over 500,000 dead Ukrainians. What we’re talking about is something that is off the charts. There’s going to be blood on American hands. If there is such a thing as Karma, the US will have a terrible bill to pay."
If you threaten to kill someone and he later turns up dead then the police will investigate you as a suspect. But the victim might have had other enemies who got him first.
As for the moral culpability, let's remember that Russia is the aggressor here. The USA hasn't killed any Ukrainians. And it's up to the Ukrainians to decide what price they're willing to pay.