It is more like going to London banker, tell them you want to make a 1 billion dollar bet on the Cubs, but you will put 10 dollars down and owe the rest if you lose. Problem if you do lose, you go to the US gov and tell them that you are about to go bankrupt and drag down the US economy unless Congress assumes the debt and dump it on the taxpayers. This is call Wall Street Banker blackmail.
But my bet is only $10, not $1 billion. And if I lose, I don’t take anyone down. Even though the nominal value is over $1 billion and I have nowhere near that in assets. Even though $1 billion is many times my family’s GDP.