Out of the choices given, the one that was NOT a contributing factor to the fall of the Roman Empire was the decline in trade. The correct answer is D, decline in trade.
According to Lafeber, this event was important for American politics because it showed that the president had much higher war powers than what was initially believed to be and the people and the congress only realized how big this power was later when other presidents started participating in wars. This was the long term effect on the US politics.
