The US doesn’t protect “money transfers” as speech as such. Buckley v. Valeo upheld limits on campaign contributions, for example. What that and Citizens United struck down was restrictions on using money to pay for political expression. If you want to spend $500 billion to put a sign on the moon that says “vote for Biden” you can do that. That’s not protecting “money transfers as speech,” it’s striking down restrictions on speech and political expression disguised as restrictions on money transfers.

Of course that makes sense. If the government can stop you from spending $500 billion to put a sign on the moon, “because money isn’t speech,” then the government can stop you from spending $500 at Kinkos to print signs for a protest, for the exact same reason. If the government can use control of money to control speech, it has vast powers over speech because huge amounts of speech involves the expenditure of money. You pay AWS to host your political site? If Citizens United went the other way, the government could control that! Indeed, during oral argument in the Supreme Court, the lawyer for the government defending the campaign finance law was forced to admit that under the government’s view, Congress could ban books by controlling corporate expenditures: https://www.supremecourt.gov/oral_arguments/argument_transcr... (pp. 26-30). (It’s one of the most devastating concessions in a Supreme Court oral argument I’ve ever read.)