Similarly qualified: Britain, Australia, Canada, France, Germany, Spain, Japan, South Korea, Switzerland, Sweden, Norway, Ireland, Iceland.
Have you looked at how many billionaires there are in Sweden and Norway? Oligarchy. Sweden has considerably more billionaires per capita than the US does. They're clearly not a democracy at all. The billionaires control the entire country including its government, obviously.
Ever look at the perpetual old money dominance in Germany and France? Oligarchy.
You're down to there only being a dozen or so liberal democracies that aren't in some way broken, severely tainted by money or entrenched power groups, etc. - if you use the same standard used against the US.