According to Wikipedia:

Americanism is a set of United States patriotic values aimed at creating a collective American identity, and can be defined as "an articulation of the nation's rightful place in the world, a set of traditions, a political language, and a cultural style imbued with political meaning". According to the American Legion, a U.S. veterans' organization, Americanism is an ideology, or belief in devotion, loyalty, or allegiance to the United States of America, or to its flag, traditions, customs, culture, symbols, institutions, or form of government. In the words of Theodore Roosevelt, "Americanism is a question of spirit, conviction, and purpose, not of creed or birthplace."

Americanism has two different meanings. It can refer to the defining characteristics of the United States and can also signify loyalty to the United States and a defense of American political ideals. These ideals include, but are not limited to self-government, equal opportunity, freedom of speech, and a belief in progress. This collection of ideals that forms the modern ideology of Americanism holds an enduring appeal to people from lands throughout the globe.

What does Americanism to a Veteran of Foreign Wars?

One only has to read the body of The Declaration of Independence from 1776:

"When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.

We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.--That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, --That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness. Prudence, indeed, will dictate that Governments long established should not be changed for light and transient causes; and accordingly all experience hath shewn, that mankind are more disposed to suffer, while evils are sufferable, than to right themselves by abolishing the forms to which they are accustomed. But when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security.--Such has been the patient sufferance of these Colonies; and such is now the necessity which constrains them to alter their former Systems of Government."

For men to believe that these same ideal are worth bleeding and dying for.  That our founding fathers would only a few years later begin the document for the basis of our nation’s government with:

We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defense, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.

Then we would test our resolve to maintain that and the union a great Civil War where Abraham Lincoln would write a recite these words:

"Four score and seven years ago our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.

Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure. We are met on a great battle-field of that war. We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.

But, in a larger sense, we can not dedicate -- we can not consecrate -- we can not hallow -- this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember what we say here, but it can never forget what they did here. It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us -- that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion -- that we here highly resolve that these dead shall not have died in vain -- that this nation, under God, shall have a new birth of freedom -- and that government of the people, by the people, for the people, shall not perish from the earth."

Finally, President Reagan said it best from the point of view of a Veteran of a Foreign War: