The Americans built the Panama Canal second. The first ones to do it were the French, but they did not finish the canal because of engineering problems and a high mortality rate because of diseases. They succeeded because the Panama Canal now makes the route between the Atlantic and Pacific Oceans much quicker, faster and convenient than if boats had to travel around the tip of South America. This allowed more places to be included in the world economy.
Turning corners in a car takes longer, and all of the cars wouldn't go as smoothly because you need to slow down some to turn a corner. Since racetracks are ovals the drivers just need to turn, which you don't really need to slow down for.
The three powerful dynasties that developed after Alexander the Great's death were. Ptolemy dynasty, Seleucus dynasty and Antigonid dynasty. For Ptolemy dynasty, they were absorbed with the Roman Empire and because their rulers were not effective, they were under control by the Romans in Egypt. For the Seleucus dynasty, they lost control over the Asia Minor against the Roman Empire and was abolished by Pompey the Great. Antigonid dynasty lost their war against the Romans because of the three "fetters" of Greece through three wars.
