How much is the US average driven down by the metrics of infant mortality? In the US we count every live birth as a birth; in many countries an infant has to breathe on its own or even survive a full day or more to count as a live birth. Counting the births as we drives down the average age.
Good point on how many countries fudge their books, making our more honest stats look bad by naive comparison. However we don't count every live 'birth.' The temporary survivors of abortion rarely get counted.