When was the last time two genuinely democratic countries went to war?

[I spent the winter writing songs about getting better]

Well, some could argue Serbia was a democracy during the Balkan conflicts of the 90s, but it wasn't actually, the elections were farher corrupt, Milosevic had things rigged his way, and even when fair elections did occur and he lost, he refused to step down until there was massive pressure put on him. I suppose it could be WWII, since Finland was technically at war with the US and Britain since they were at war with the Soviets who were allied, but no battles between the Finns and Americans or Brits happened.

[I spent the winter writing songs about getting better]

Never.  Wars are invariably caused by dictatorships.  Democratic societies never choose to wage offensive war, because most people don't like war.

I would probably never support a war against a true Democracy, and there would probably never be a need for one.

Then I guess you weren't a fine of the US executing a coup in the democratic nation of Chile, or funding rebels against the democratic nation of Nicaragua, or the plans to invade Italy if the Communists ever won the election.

[I spent the winter writing songs about getting better]

Iraq posed no threat to the US. And there's no way you can even argue Vietnam posed any threat to the US.

[I spent the winter writing songs about getting better]

You're probably thinking of Finland, during WW2. That's because Finalnd was fighting the Soviet Union and allowed the Germans to set up air bases on their land to launch sorties against Soviet forces. British forces never actually fought Finland though, they simply attacked the German air bases. Now it's also worth pointing out Finland did join the Allies in the end, once they fended off the Soviets the Germans refused to leave their territory. So Finland declared war on Germany and fought to force them to leave.

[I spent the winter writing songs about getting better]

Iraq posed no threat to the US. And there's no way you can even argue Vietnam posed any threat to the US.

Vietnam was a proxy war, and the belief was that the ideology represented by the North Vietnamese posed a threat if it spread.  This is not a black and white issue, but suffice to say there would have been no war had the North Vietnamese not sought to take over their neighbors, which they eventually did.  Obviously, we made our share of mistakes.

Iraq once again is a war against something larger - the Islamist terrorist philosophy and the deadening repressive middle eastern dictatorships that result in terrorism.

There was no threat from a comunist Vietnam, as we see ther ewas no spread throught SE Asia.

Iraq was not an Islamist dictatorship. Saddam hated Islamists and was very secular. Islamist Iran sure didn't like him.

[I spent the winter writing songs about getting better]

I guess the War of 1812 counts, if no one has said that yet.

Wasn't Britain still largely controlled more than the monarchy than any democratic leaders then?

[I spent the winter writing songs about getting better]

There was no threat from a comunist Vietnam, as we see ther ewas no spread throught SE Asia.

Cambodia, Laos?

The communist takeover in Laos was largely due to the instability in the region created by US bombing, and it's not like Laos is any threat to the US.

That is also true of Cambodia, but using that as an example is fairly ridiculous considering it was actually the new unifed communist Vietnam that ousted the communist government.

[I spent the winter writing songs about getting better]

One could make a case for the American Civil War, since the Confederacy had a Constitution set up for a democratic system of government.

However by today's standards the Confederacy was not democratic due to the enslavement of a large portion of the population. But of course the Union wasn't truly democratic back then either.

[I spent the winter writing songs about getting better]

Here's one I thought of: The Arostook War, although that was actually fought between a US state and Canadian province, Maine vs. New Brunswick. Of course no one died.

How about that war in Central America that started over a soccer game?