Dear questioner,
I do not personaly agree that if we had not entered a war in the past century, we would not be currently speaking English.
Starting with World War I, if the Allied powers had lost, the United States would have been the least affected. Unlike many of our European allies during the war, we did not have a large collection of over seas territories. The Central Powers would most likely have asked for possesion of most or all of the Allies colonies. Being that we did not have as many as say the UK or France, this would not have affected us a great deal. Also, the United States, Japan, China, and some Latin America and Carribean countries were the only non-European countries of the Allied powers, so it would have been hard for the Central Powers to conquer and control us without raising large armies, which would eventually have led to the conscripting of people from the mother country and new and old colonies. The conscripting of people might work for a short period of time, but depending on the length of the invasion, the resources would eventually exhaust or the people could revolt.
A very funny thing, if you look at it, is that if we had lost WWI Japan and Italy, countries of the Axis Powers during WWII would have also lost to Germany, and if WWII would have happened when it did these two countries would be enemies of Germany not allies.
Moving on to the Korean War and the Vietnam War, these were conflicts under the larger caption of the Cold War. The Cold War was just a big misunderstanding. The Russian's history has been full of invaasions from foreign powers. This has created in them a inherited fear of foreigners who are powerful. With the United States becoming as powerful as it is, their natural assumptions were that we were preparing to invade. To the United States, the USSR was stockpiling nuclear weapons and spreading it's influences throughout the world in an attempt to "control" the world. in reaction, the United States formed alliances with countries situated around the USSR (Japan, Pakistan, NATO, ect.) in an attempt at containment. To the USSR, this look like a noose that could tighten any minute.
The firsr Persian Gulf War, was an attempt by Saddam Hussein to control the oil fields of Kuwait. We and a coalition of nations repelled his attacked. Mow if Saddam had been smart, he would have struck a deal with North Korea and launched simultaneaus attacks and thus spliting the US forces. Victory for Saddam and North Korea would have resulted in dominance of oil production in the Middle East by Saddam and a united Korea under Kim Jong II. Neither Saddam or North Korea would have been capable of invading the United States.
Finally, the United States is a country of many languages, and usually a conquered people do not give up their native language as an act of defiance.
Sorry about the lengthy answer. It was a good question and I enjoyed answering it.