Ok, let's see if you can understand this. The balance sheet of the central bank is like this. The currency issued by the central bank is his debt, and he uses the issued currency to buy American treasury bonds, which are his assets, so that the assets and liabilities are balanced. The act of buying government bonds is QE, which is equivalent to the Federal Reserve putting its own money into society by buying government bonds.

Due to the implementation of several rounds of QE, the Federal Reserve issued a large amount of money (liabilities) and purchased a large amount of national debt (assets). Therefore, the Fed's balance sheet is seriously inflated, and now the Fed is considering shrinking its balance sheet and reducing the money supply.

The huge liquidity brought by QE really devalued the dollar. If you look at the US dollar index since 2009, this is very clear. But it's not that simple. The depreciation of the dollar depends on which currency it depreciates. Since the financial crisis, major countries have been competing for easy money, and now these countries have begun to gradually reduce easing together, so it is somewhat arbitrary to judge the appreciation of the US dollar directly. This problem is really complicated. If we can figure it out, we can make a lot of money by buying dollars directly now, haha.