Finally arrived on Friday, March 25.
I see that it came "Standard Mail" which was the reason for the time delay; it took 15 days to get to my mailbox. Those who reside overseas probably had theirs sent by first class which explains why those in France received theirs on March 20.
Standard Mail (domestic use only), also known as "bulk mail", is processed by the USPS on a “time available” basis. Standard mail is not forwarded or returned if undeliverable unless a special endorsement is used. Standard mail will typically be delivered in under 5 business days locally, but nationwide it could take 2 to 3 weeks. Standard Mail should not be used for time-sensitive mail. As with Presorted First-class, to receive the lower postage rate, the addresses must be NCOA updated, CASS certified, and put into presort order.
Standard Mail is the least expensive postage mode, approximately 32 percent less than the price of first class. Standard mail postage rates apply to mail up to 3.3 ounces. Mail heavier than 3.3 ounces will have a small weight surcharge.