Citizens United case means that, by design, there will be no evidence of money transfers from foreign powers to US elections.

so the idea we can 'find no evidence' is because people rigged the system so there would be no evidence.

Democrats could start taking money directly from Xi Jingping or from some communist in Venezuela and we would never know about it. Republicans can take money from the Saudis and we would never know about it. This is the reality of modern politics in the US.

infinite invisible money and zero evidence that anything happened, by design