A demographic death spiral happens when there are too many people older than working age and they receive entitlements. Younger people leave rather than fund a bunch of seniors. Avoiding an aging population is the only way to stop a demographic death spiral.
We are not in a demographic death spiral. The median age in the US is 38.5, which is 61st in the world. China is 38.4, which is 62nd in the world. India is 28.7, 141st.
The total fertility rate in the US is 1.84. In China, it is 1.6. Do you think China is in a demographic death spiral? China is still growing at .26% a year compared to our .7%. China has 1.4 billion people. We have 332 million.