In Oz if we are sending parcels overseas, and can't afford to send by airmail and have to send by sea then we are told to allow a few weeks for the U.S. and the Brits & Ireland. Maybe 4 weeks if you are optimistic and 6 is a fairly safe bet.

If it gets there earlier than that then it is the luck of the draw, because they usually have to wait until the container is full enough to make it worthwhile to send. It used to be that ship mail ("whale mail"?) was the most common and therefore it was sent almost as quickly as you posted it. Now airmail ("albatross mail"?) is more common and so there is no delay in actually getting it in the air.

Airmail can be sent economy rather than premium in Oz and this can add a few days to the arrival time. Airmail letters I have sent to the U.S. have arrived within 10 days usually, and 7 is the record for me.

Helen