> but chose to keep the citizenship into adulthood, presumably acquiring a passport or other citizenship documents
That is ... not how citizenship works. Once you are a citizen, it can be very difficult to get rid of that status (souce: born in the US, will end up paying an arm and a leg to get rid of mine). Failing to get a passport, file returns with the IRS, etc. can lead to you getting ignored, but it can also lead you to getting into serious hot water in the future.
Example: most passports list the place of birth of the holder. If you are an American citizen, you must enter the US on a US passport. Because of American citizenship law, someone trying to enter the US on a Dutch passport with a place of birth listed as being in the US is going to have to do some explaining, and possibly provide documentation of renouncing their US citizenship. "I never applied for my American passport" is probably not going to cut it. It's a huge pain!
> Also as far as owing onerous back taxes go, aren't taxes you paid in your country of residence deductible ? For most EU countries wouldn't that result in net zero US taxes ?
It depends! But you still have to file, and there are still penalties for filing late, and even if you do, IRS reporting requirements to other banks mean that many European financial institutions won't touch you with a 10-foot pole no matter if you are also a European citizen.
Ones that will (like my bank), still won't offer you much beyond current account services and a basic savings account. If you want to do any kind of real saving for the future or basic investing (ETFs, for example), you are going to have trouble. The supposed disruptors in the market for this kind of thing (Trade Republic etc.) certainly don't have the resources or the interest in dealing with you either.