That's not even the real problem, though. The problem is that banks don't want to deal with the FATCA compliance issues and just refuse to deal with Americans, period. I've experienced this firsthand as an American expat and it is a colossal pain in the ass.
[1] https://www.irs.gov/individuals/international-taxpayers/fore...
There is no official guidance to FATCA and its processes, and every country has passed its own FATCA related regulations. Therefore running a FATCA compliant entity in say france requires you to comply with all french laws around fatca. Which also leads to issues with GDPR. This creates a cost of several hundred thousand USD per year just to deal with US clients for most western finance companies, per country they do business in.
Or - simply flatly refuse to offer services to any US citizens and rest easy knowing the IRS isn't going to ruin your life just because a US citizen tried to open an account without even depositing a single cent, but you didn't file your IRS stuff correctly
For example, if you earn 200k in a foreign country and that country charges you 75k on 190k of that, and decides that 10k doesn't count for some reason. Suppose the US rates are such that you owe 60k on 190k, then the FTC erases that 60k. But you might still owe 3k on the remaining 10k that the foreign country ignored.
So, if you happen to be an expat in a higher tax country (which is certainly Europe), then you won't owe taxes in the US. You still have to file, which can cost $500 for an accountant to make sure everything is correct, but owing taxes isn't really an issue.