The distribution of vaccinated people is really uneven in the US and the states that have the most vaccine-resistant population also have officials who are not making much of an effort in vaccine outreach, so it's a bad combo. And even in states where vaccine uptake was initially quite high, it's reached a plateau that is only going to increase marginally unless more vaccine mandates are put in place (which they are).

But I think the 80% number is percentage of eligible population. For the total percentage of all Australians it is 66% compared to 65% in the US for at least one shot, so not much difference at all. I've noticed that a lot of times percentages are reported as percentage of the eligible population without mentioning that that's what they're doing, so it looks higher than it is.