Cataclysmic news. The government needs to implement policies to reverse this ASAP lest we fall into Japanese style stagflation. Our future economic success depends on population growth and this issue should be treated like the national emergency it is.
As bad as Japanese style stagflation is, raising populations eternally is most certainly not sustainable in the long run (this applies to the US and to the entire world, it's just that developing nations have ridiculous birth rates still while the US are just barely below the ideal)
Immigration is also not a solution. It's a bandaid at best that can't really solve anything long term and has its own set of problems as well.
The only solution is to completely overhaul the economy so it is actually sustainable. How to do that of course nobody knows.
Also overhaul the money system so it's sustainable as well, which might actually be the bigger problem.