Because Treasuries are the foundation of the global financial system, and there's basically nothing that could replace them completely.

It seems like it would be a good idea to move the global financial system off the shaky ground before it opens up into a bottomless sinkhole, but what do I know about global finances?

Where do you put all the money? If there was a deep and liquid euro market, or if China removed capital controls then maybe.

The question doesn't make sense. Money can't be "put" in places - it always circulates.

OK, so I have $1 trillion in Treasuries, and I sell them. What do I do with the cash? Presumably I'd like other government debt. The trouble is that I need to put this into another market, so what do I choose? The total euro government bond market is 8 trillion euros, so I'm probably gonna move that market in a way that's not good for me. That's the point I'm trying to (badly, apparently) make.

Am I missing something here?

The act of selling them distributes money from someone else to you.

I recommend productive investments. Whatever the other person who had the money was doing. Growing corn, for example, or making cars.

I'll be sure to tell most pension funds and insurance companies that they should change their investment strategies, thanks!