The Reign of Terror came to an end, because the man who had started the Reign of Terror (Robespierre) was executed. The Reign of Terror also came to an end, because nuns had been executed because they did not want to give up their monastic vows and they were very calm during the execution, so this shifted the mood in Paris, probably making the general population realize that the mass executions were futile.
Answer: America sought to impose itself as a world power.
Explanation:
The reason for joining the united states is the effort to impose itself as a world power after decades of isolation. In that direction, they acted to exploit the revolution in Cuba that the population sought to achieve because of Spanish dominance. So the cause was the Cuban Revolution, and the real reasons are the effort to make the country stand out on the international front as a vital force.
Many riots and internal problems weakened the Spanish. In such circumstances, America wanted territorial expansion. The end of the conflict brought Cuba independence, but Cuba was under US jurisdiction. The Philippines, Guam and Puerto Rico have become parts of the United States.
Although it's a bit counter-intuitive, Columbia actually never explored North America, instead visiting the other locations on this list instead. This lead to great discoveries but lots of suffering for the local inhabitants.
<span />