[cperciva]

US taxation applies to dual citizens who don't hold US passports though.

Heck, it applies to people who don't even realize that they are US citizens -- a number of Canadians have been hit by large bills from the IRS after discovering at advanced age that they have a parent born in the USA.

[davchana]

To add more to your point, if one has unknowingly US citizenship (through parents at birth or something) && a local citizenship (where one is living, like India, Canada, UAE, anywhere), that host country is not going to give same protections as compared to somebody with "only" US citizen. For example , US citizen having Iranian Passport in Iran are simply Iranian citizens in Iran Government eyes. (Replace Iran with any country). US citizen working/visiting in Canada, but having no Canadian citizenship, can go ask US embassy in Canada for help.