I remember a bunch of Americans telling me that America isn't a democracy, and shouldn't score high on those indexes that rank countries... because the USA is actually a republic.
So of course, there's no sense in comparing the US to other countries unless they're also republics. Or if we're talking about economies.
Countries and their governments are never cut and dry.
If we're getting technical (which I hope we are) then the United States of America is a presidential, constitutional representative democratic-republic that permanently federates and holds legal supremacy over a collection of similarly stylized democratic-republic states (along with other colonies, territories, and possessions). All of this is technically correct, but it isvery hard to fit on a bumper sticker unlike the flashy fascist conservative think tank sound bite of "wE'rE a RePuBLiC nOt A dEmOcRaCy."
Mmm, not really. The structure has a lot of mistakes in it by virtue of being the first modern democracy. For example, the Senate giving every state two representatives regardless of size.
Most other democracies opted for a parliamentary system, where the chief executive is also the head of the legislative branch. This includes democracies where the United States was directly involved in setting up its structure, like Germany, Japan, and Iraq. Our crazy system should be taken more as a warning than an instruction manual.
There are federal elections (of a sort) so the country as a whole can be gauged on that. And on that front... not looking so hot, either, but it's not as bad as certain individual states.