The Federal Reserve is a US government created organization, with specific public mandates, and has the full backing of the entire US and global financial & monetary systems.

Tether is a private company, controlling $67B in assets, with less than 10 FT employees, a CEO who hasn't been seen in public for years, with no transparency into their backing, has been caught lying multiple times in court, and has been involved in multiple civil and criminal investigations.

There's no comparison.

full backing with what exactly? You are joking right? Only powerful US army is backing it, nothing else.

Oh that's all.

But wait, what about the Navy, the Air Force, and the entire US economy?

The vested interest of many countries

the fed never promised they were backed by cash

Also, the Fed doesn't print money to buy coke in hookers.

It prints money so the US government can use it (you can argue to what degree that is waste).

But the Fed's balance sheet is solid and highly liquid.