Currency is already managed by the elected government, and every democracy in the world traces electronic transactions. Some (like Italy) forbid cash payments in large sums altogether. So what's the boogieman here?

The boogyman is just what you described, and every democracy in the world absolutely does not trace electronic transactions.

Some have a more hands off approach, including size of transactions and flagged behaviour as indicators of when payment processors must report to the government.

The Goverment should absolutely have no idea who spends what, where. Warrants and court orders, check values should be required before anyone can know. The potential to suppress political opponents, to squelch legitimate protest, to interfere with elections, is too dangerous.

Simply because some countries, like the US after 9/11, decided to give up this aspect of a free people, does not make it right.