"We need immigration to compensate for low birthrate" lie

The low birth rate extending perpetually unless we add immigration is incorrect.

We have a weighted average of groups with different birthrates. Over time the aggregate average will increase to a growing population level due to high birth-rate groups (ie conservative Christians, especially groups like the Amish) becoming more numerous and having a higher weight in the average. It is trending down temporarily because of the abrupt change over the last ~10-20 years of mostly liberals to stop having children. Mathematically, the total TFR will trend towards the TFR of the highest groups as they grow more numerous in comparison to other groups.

Bottom line - the fertility rates for the whole country don't represent a homogenous population and therefore we don't need immigration to bring up TFR. We just need the left to continue to erase themselves from existence and conservatives who have children will then become a larger share of the population