A below-replacement birth rate might be a good thing IF the borders were closed. With the borders open, a low birthrate results, not in population reduction, but simply population REPLACEMENT.
Well yes, that's what I'm saying: we don't have the problem of a mushrooming birthrate.
But the only reason we have a problem with mushrooming population growth is from immigration of ALL kinds.
Perhaps if this country were a nicer place to live with plenty of room and fresh air for its citizens instead of being shut into densely populated cities, people might feel more normal and start to have babies again.
But if people continue to live apart from nature, you can expect them to think unnatural thoughts and to do unnatural things, like not have babies.