These threads seem to appear every few months. They're always interesting. My spouse and I have dual Brazil/US citizenship and use Brazil for everywhere that we do not need a visa, US where that confers a benefit. Even after SecureFlight it has been no problem. On my last trip I presented the brazilian ones by error to check in in the US and was told "we need your Brazilian ones too". Both are in the profile.

For people who consider getting US citizenship it is good to remember that you'll then be taxed on your worldwide income regardless of where you live. That is why there's a long wait for an appointment to renounce US citizenship in most US Consulates, and even then you'll be subject to US taxes for, if I recall, ten years after renunciation (I have no idea how they'd collect that. Of course once on renounces US citizenship one has a hard time getting a visa to return, so 'they' say. Anyway, think carefully before you choose to naturalize in the US.