I would agree, send is usually a transitive verb, and the sentence is not grammatical. Meriam Webster lists 2 intransitive version, usually follows by "away", or "out", (so send away or send out), but neither seem to be relevant here:
However I don't think that is the problem with the sentence.
The problem is that the subject of send should be the person/group/thing that is doing the sending, and the objects are the item that is being sent (the parcel), and who the item is being sent to. So for example, we can have "Alice sends flowers to me". Alice is the subject, and the objects are the flowers, and me. The second object (me) is optional, so "Alice sends flowers" would be grammatical.
However, in this sentence, the parcel is being used as the subject, which is incorrect.
I think the sentence should use sent, and look like "The parcel sent to the USA, Italy, Australia and Japan which not up to 2kg...". That specifies a particular set of parcels, and the rest of the sentence specifies what happens to them, in particular that they are treated as if they weighed 2kg.
I think the sentence should be
Parcels sent to USA, Italy, Australia and Japan which weigh up to 2kg will be treated as weighing 2kg.
user8543 also has a reasonable translation.