Like most of the world’s large economies, the U.S. does not have a currency board. In the United States, the Federal Reserve is a true central bank, which operates as a lender of last resort. The exchange rate is allowed to float and determined by market forces, as well as the Fed’s monetary policies.
By contrast, currency boards are somewhat limited in their power. They mostly just hold the required percentage of pegged currency that was previously mandated. They also exchange local currency for the pegged (or anchor) currency, which is typically the U.S. dollar or the euro.
A currency board has less power to harm or help the economy than a central bank.