In Flanders field the poppies blow...Nationalism and the lessons of WWI

One hundred years ago the United States of America reluctantly ended its isolationism and joined WWI against the Central Powers.  At that point, WWI had raged into its fourth year, with the dead and maimed growing each day, millions upon millions.  Nobody knew it at the time, but WWI only had a year and a half until German exhaustion brought it to an end.
WWI was not an example of Just War Theory in action, at least not for its principle protagonists, the Great Powers of Europe who went to war for nationalistic reasons, each hoping for a quick victory that would increase their relative power and prestige at the expense of the enemy.  Nationalism had helped turn the kingdoms of Europe into modern nation-states, but it also stoked hatred of the "other" (Germans of Russians and the French, the French of the Germans, etc.) and enabled leaders to whip up war enthusiasm by painting the enemy as evil.
I've written this before, but it bears repeating, nationalism is not compatible with Christianity.  Patriotism certainly is, if your city, state, or country is lovable, then by all means love it and be proud of it.  Nationalism is different.  Nationalism is the belief that your people are superior, and thus other peoples are inferior.  When it puts down roots and matures, nationalism views the people who are not like us as a sub-human or inhuman "other".  This false pride and denigration of other peoples is contrary to the clear teaching of the Gospel that all men are created by God and that in Christ there is no slave or free, no Jew or gentile, all are one in Christ.  The British, French, German, Austrian, and Russian soldiers who went to war in 1914 were largely Christians, and yet they fought against their fellow Christians, replacing brotherly love with gruesome killing, because they had been taught that their enemy was not their brother in Christ, but instead a fearsome "other".
WWII saw a reprisal of nationalism, brought to its ugly natural culmination in Nazi Germany, before it was discredited by the deaths of tens of millions in that war.  After WWII, nationalism lay dormant during the Cold War, as the battle between Communism and Capitalism took center stage, but following the collapse of the Soviet system, it began to grow once more.
Nationalism is on the rise, in America and Europe, moving us back toward an era of "us not them", of dangerous competition instead of cooperation.  Will the world forget the horrors of WWI and WWII?  Will the lessons paid for in so much blood and destruction be ignored?  A pessimist would see the return of nationalism as a natural counter-balance to the free-market and open-border policies of the recent past, and would resign himself to a return of the dark days of national rivalries.  An optimist might see that same return as an opportunity for the nations of the world to show that they are capable of learning from the past, only time will tell if optimism or pessimism is warranted here.
The Church and Christians in general were fooled by nationalism before, allowing the us vs. them mentality to replace what the Word of God declares about Christian brotherhood and the dangers of pride in oneself and hatred of one's enemies.  Let us pray that the Church and the Christians within her will be wise enough this time around to say "no" to the siren's call of nationalism, for all the world's people have but one Father, one Creator, nobody is an "other".