[Ajedi32]

The US is a democracy, so Americans are, at least on a collective level, responsible for the actions of their government, though not on an individual level of course.

Iran is a theocratic autocracy. Only the autocrat and his supporters bear any significant responsibility for the actions of the government there.

[nmilo]

In theory sure but in practice not really and to say regular citizens have a direct say in specific geopolitical decisions is absurd, given how unpopular many recent decisions have been.

[tgma]

The US is not a democracy, by design. It’s a Constitutional Republic.

[Ajedi32]

A democratic constitutional republic. Often simply referred to as "a democracy" as a shorthand.

The key distinguishing factor being that in a democracy powers are derived from the consent of the governed, as opposed to other forms of government (including some "constitutional republics") which do not allow open democratic elections.

[tgma]

Citation needed. Where did you get that additional term in front of it? Which United States founding document suggests that?

Democratic Republic, just like People's Republic, is actually a euphemism for communism.

What you are describing is "representative government" and "self government" not necessarily democracy. The will of the people is an abstract concept that is, depending on the issue, not always accurately measurable by equally weighted vote of a subset of the people that are enfranchised.