Presidents don't have a monopolization on power (in the US);

Of course they do. Just because they "share" their power with a government, doesn't mean the government doesn't monopolize power.

Also, the US already had a confederacy, and it didn't work out so well (even ignoring slavery).

Please read up on what "democratic confederalism" means. It's not comparable to what the so-called US did (at least after Europeans arrived - the Iriquois confederacy is more like it).

The so-called US was always focused on giving power to capitalists, while democratic confederalism is fundamentally socialist/usufruct.

This is beginning to look a lot like it relies upon human goodwill and good faith participation, and it appears like it would be easy to exploit by a bad actor feigning innocence; as we've seen throughout history, there's no shortage of selfish opportunists.

You've got to realize that the current system is de facto succeptible to these bad actors by enabling them to amass power, right?

There will always be a leader(s) at the top, even in a confederacy or a union. You need visionaries, and humans, like other apes, are naturally inclined towards having leaders and being told what to do (it saves mental energy for survival).

I don't think that's true. I think that's a narrative that's very convenient to the powerful but not at all necessary. And there's anthropological evidence that political hierarchies aren't necessary in society.