A lot of nationalist Americans think this way, yes, but they do not represent all of us. They merely get the most sound bites broadcast, hence why foreigners think *all* Americans are like this, when in actuality it's probably less than 50%.
Some Americans are heavily blinded by their own ignorance of history which is a product of a poor public education system. I didn't learn the truth about the reasons behind Japan's attack on Pearl Harbor, or why the US really dropped two nuclear weapons in Japan, or why the US got involved in Vietnam, or even America's Civil War until I was in college, and I'll be honest with you, I was pissed off when I figured out how I had been duped with American superiority propaganda from my 12 years in public schools, and it's why I'm so cynical about it now.
Even the number you quoted for WW 2 is not necessarily incorrect, but it is misleading. That 70 million figure is for ALL deaths, civilian and military, for ALL nations involved in the war. The Soviet Union suffered the most military casualties at somewhere between 8.6 million and 11 million dead. By contrast, the United States lost less than half a million. So it makes my blood boil to hear ignorant people claim the United States won World War 2 as if everyone else just stood by and watched. In reality, if it had not been for Stalin beating back the German invasion of the USSR, the result of the European war would have turned out much differently. If any one single country deserves credit for the defeat of Nazi Germany, it's the Soviet Union, not the United States.
For those of you just tuning in, America is not the greatest country on Earth. Never has been; probably never will be. Americans are brainwashed almost from birth to believe this, but not all Americans are drinking the kool-aid. So give some of us the benefit of the doubt.