Yes you can get a tracking number. You can send a letter by post to the US with a 3 day guarantee for $50 that comes with a tracking number.

If you send a letter regular post but registered with a tracking number it takes about 10 days but if the letter is lost you can't track until it has been lost for 30 days ( I am pretty sure that is the deal.)

You can send a letter by FEDEX at Tropic Air - takes about 4 days to the US and can be tracked. Cost around $80

And packages/boxes etc just cost more based on DIM.