I think WW3 will start in Russia or North Korea because Russians are threatening to fire missiles at Poland and Lithuania and North Korea test fired short range missiles one again.
The panama canal helped america and other countries by making the shipment of goods shorter then going under South America, and It helped America by having the countries paying tolls to get though the canal.
It may have caused problems but then it helped us in a way because when there was a war countries wanted us to be on their side and every war we had helped a country we have won.
The way WW1 was fought was out-dated because they were using tanks, gas, machine guns, rifles and mortars and If you were one of the men that charged then you most likely would have been killed.
In the past we had to be imperialistic to be able to survive in the world because then countries would fight us to try to conquer us and by fighting other countries it showed we were the country to beat.