Answer:
The nation and the nationalism.
For Europeans, the effects were mostly positive. They experienced an overpopulation problem as well as monarchic and religious tyranny and were under the constant threat of Islamic invaders. One of the main reasons why Columbus wanted to find a way other than Cape of Good Hope to get to Asia was that Ottoman Turks had blocked all access to Asian trade and travel.
The Portuguese had a monopoly on the Good Hope route and this route was actually too long. When Columbus discovered the American Continent, he thought he had actually found Asia. In any event, Europeans found a land that they could conquer and colonize, they sent all their excess of people there. They found valuable raw materials as (timber, gold, silver, iron, etc.), spices, exotic fruits and vegetables (tomatoes, potatoes, avocados, etc.) and eventually used to Continent as a gateway to Asia.
For the Natives of the Americas, the effects were disastrous; most of them were wiped out by diseases unknowingly brought in by European explorers or colonizers. Several others were subjugated or even exterminated. Their most powerful empires were vanquished and conquered (Incas, Aztecs) and the land they had found several thousands of years ago became European. There were however, positive aspects in their disaster. They had access to Western civilization, science, culture and technology. They discovered Europe as much as Europe discovered them. Many of them discovered writing (many had already some form of writing but other indigenous cultures were exclusively oral). They also had access to the modern concept of nation-states (like the Five Civilized Tribes in the US).
For Black Africans, the results were mostly disastrous. They were captured or bought from other African slavers by European Slavers and suffered slavery for centuries before they were eventually integrated into society. However, they also enjoyed – though marginally - some of the positive aspects mentioned earlier for natives of the Americas (access to Western civilization, science, culture and technology).
Ayatollah Khomeini lead an opposition movement in Iran against Reza Shah Pahlavi to overthrow the authoritarianism type of government that the people disliked and create a new government. The people were fed up with the rule of Pahlavi and they wanted the change. Ayatollah Khomeini took advantage of this mood and returned to his country from exile.
