“just what kind of “money” is so-called “real” US Dollars”
Freely exchangeable and internationally accepted.
Dollars are the reserve currency. And right now the UST is the most popular bond in the world. You need to buy it with dollars.
So, the Treasury is collecting all of the dollars, sucking them out of the system. This means that companies that need dollars to transact with are having to pay greater prices for them. This is inflationary everywhere but in the US. For example, the price of gold has reached new highs in non us currency. This is the problem with a strong dollar.
When a large economy decides to trade in something other than dollars...the chickens will come home to roost. And that will be a bad day for us. But, right now, there are few alternatives.