On Wednesday, 01 July the Royal Mail will increase the cost of sending small parcels airmail to the USA. This is due to unilateral moves by the USA to increase its charges to other members of the UPU. So if you are in the USA and thinking of ordering June would be a good time.
This price rise only affects parcels sent to the USA that are more than 25 mm deep (so called small parcels). However, it is a significant change because it's a large one: an increase of between 40-50%.