[saalweachter]

It's just that in the US, there are 3.6 million babies born each year; even taking the low-end of a $500k one-time payment to one parent, you're already talking a $1.8 trillion / year program, slightly larger than Social Security's $1.6 trillion program.

Social Security is funded by a 12.4% income tax, with half nominally paid by the employee and half nominally paid by the employer.

You'd need a similar tax to fund such a benefit, which would amount to a 15% income tax, assuming the program isn't too successful in raising birth rates.