In the 1670s, the first significant groups of German immigrants arrived in the British colonies, settling primarily in Pennsylvania, New York, and Virginia. Immigration continued in very large numbers during the 19th century, with eight million arrivals from Germany.
Spanish conquering Mexico
Effect: Death of 2 continents. Deconstruction of thriving civilisations. 2 brand new continents for Europeans to put to use.
Cause: The Spaniards wondering if the Earth is actually round. During the journey the stumble upon the New World. Another cause is the greed and disrespect of the Spanish colonizers. The American natives were seen as primitive and savage, which the Spanish saw as a reason/excuse for killing their cities, people and culture.
Depends. What war are you talking about? If it's WW1, then it's because everyone was stupid at the time and thought their enemies did it and one thing led to another.