Then compare the Queensland-NSW border or the Victoria-NSW border, probably comparable with most European borders or at least within 1 order of magnitude. Both

Then compare the Queensland-NSW border or the Victoria-NSW border, probably comparable with most European borders or at least within 1 order of magnitude. Both borders were closed (with exceptions) at various times to contain outbreaks to one state. If we loosen up the definition of country then these are Western countries that aren't island nations with zero covid. It shouldn't also be noted that the borders don't have to be hermetically sealed. As long as cross border contamination is minimized other tools (contact tracing) can deal with it.