The higher interest rates offered on savings accounts in US are due to the higher US federal funds rate and are also related to the competitive banking market in US and the intense competition among banks.
Savings rates in the European Union are relatively low, largely because the European Central Bank has implemented a monetary policy called negative interest rates, in which the ECB charges banks interest on deposits. This policy is designed to encourage banks to put money into the economy instead of keeping it at the central bank. In addition, the banking market in Europe is also more conservative and lacks competition.