> Yeah, the US and Canada are the only two first world countries not slated for long-term population decline due to immigration.
Australia's immigration rate, on a per capita basis, is more than double that of the US, and somewhat ahead of Canada's. [0] It has a lower total fertility rate [1] than the US (1.73 for Australia vs 1.84 for US), but still a higher TFR than Canada (1.57), and I suspect having double the immigration rate is probably going to make up for the somewhat lower fertility. And I think you are missing more countries than just Australia.
While in absolute terms, the US accepts more immigrants than any other country in the world, on a per capita basis, its net immigration rate isn't particularly high, and is below that of many Western European countries.
Likewise, US total fertility, while high by Western standards, is not the highest in the Western world; France is significantly higher at 2.02; Ireland and Iceland also beat the US at fertility, and Norway is only just behind the US.
[0] https://www.cia.gov/the-world-factbook/field/net-migration-r...
[1] https://www.cia.gov/the-world-factbook/field/total-fertility...