Christopher Columbus was on a voyage trying to find a direct route from Europe to Asia but he ended up discovering america and the native Americans who lived there at the time. Some reasons he stumbled into this place instead of where he was originally trying to get (Asia), First he got the wrong map the old map the one that he got didn't even have america on it, because the map maker that he called only makes maps from what hes heard from Columbus's voyages around the world. Secondly Columbus also claimed that he knew a shortcut to the spice islands, Lastly Spain agreed to Finance Columbus voyage. After that he landed in the Bahamas but he believes it to be the east indies which is why when he meets the natives he calls them Indians. He also ended up discovering a whole new world but died before he could realize this, and finally he opened up the world of trade for everyone.
In 1453 Constantinople falls to the Turks, A couple reasons they fell was one because the turks cut off their supply of spices which they used for food and where they made most of their money, There army (The byzantine army) was also very small and reduced due to the black plague, and lastly their main defense was the walls that surrounded the city which they ended up being to dependent on. The fall also ended what was left of the roman empire, it also set a giant roadblock in all the trade, And finally Constantinople was the only thing that had held back Muslim invaders from evading Europe which ended after the fall so they were all free to invade the Europeans.
The Spanish armada was a Spanish fleet of ships going to invade England. Elizabeth aided Dutch Against Spain which angered Philip, Philip was also humiliated by Elizabeth because she rejected his marriage, So Philip laid plains to go and invade England, Which leaded to the English being victorious which then opened the door to English and french colonization of north america. It also caused the Spain to decline because they used most of their resources and money on forming the ships, which lead them to stealing and looting other places and city's.
SOURCES: Notes, history.com, www.enotes.com, Answers.com