Most people won't have sufficient income to be double taxed but it is a concern. From the IRS "If you are a U.S. citizen or a resident alien of the United States and you live abroad, you are taxed on your worldwide income. However, you may qualify to exclude your foreign earnings from income up to an amount that is adjusted annually for inflation ($105,900 for 2019, $107,600 for 2020, $108,700 for 2021, and $112,000 for 2022). In addition, you can exclude or deduct certain foreign housing amounts" -- https://www.irs.gov/individuals/international-taxpayers/foreign-earned-income-exclusion
In addition, while I don't know about Canadian banks, European banks don't like dealing with Americans due to reporting requirements set by the US government, so it can get real difficult to live abroad as a US citizen. It becomes a messy maze of regulation real fast.