If God forbid,your son is again stung be a wasp,then look out for the symptoms.It can occur as allergic reaction or a serious anaphylactic reaction. An allergic reaction may include hives or rash, swelling away from the sting site or headache. These allergic reactions are not life-threatening and can be readily treated with an antihistamine.
However,if it is an anaphylactic reaction ,then there may be fainting, difficulty breathing, swelling, and blockage in the throat within minutes of being stung.Then epipen should be administered immediately and your son should be immediately rushed to the ER.
Same is the mode of treatment even if you move to other countries.To your query about whether he may be allergic to wasps and bees in other countries,then it is very difficult to say anything without allergy testing.You can get your son allergy tested by an allergist for the different wasp or insect stings and then avoidance of these will be the best treatment.
I hope that helps. Please do keep me posted on how your son is doing or if you have any additional doubts.Warm regards.