Many countries have tried giving every incentive possible. Cash bonuses, tax breaks, a year+ of mandatory child leave for both men and women, cheap child care, mandatory flexible hours, housing subsidies, cultural campaigns.
Some of them have a short term effect but none of them get the numbers up to replacement levels and the numbers keep going down.
It's hard to blame it on any one thing. Some might say "suburban car centric culture" but that doesn't explain Japan, Korea, Singapore, etc....
I can't personally imagine the numbers going back up.