Proposition Nation v. Preposition Nation

On the White House webpage regarding immigration and amnesty, we read President Obama version of the conventional propositional nation wisdom that emerged a decade or two back to justify de facto open borders:

Fixing the Immigration System for America’s 21st Century Economy 

“We are the first nation to be founded for the sake of an idea—the idea that each of us deserves the chance to shape our own destiny. That’s why centuries of pioneers and immigrants have risked everything to come here…The future is ours to win. But to get there, we cannot stand still.” 

-PRESIDENT BARACK OBAMA

 

The “propositions” are usually taken to be from the Declaration of Independence:

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.

Yet, as Abraham Lincoln and computer scientist John McCarthy have implied, there appears to be typo left in during the rush, and that the Declaration would make far more sense if it read:
We hold these truths to be self-evident, that all men are created equal, in that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. …

(It goes on to list a number of other truths.) 

In any case, there are other Founding documents that, for some reason, don`t get cited much by the Propositionists, most notably the Preamble to the Constitution, which puts forward a carefully considered explanation of what the United States exists for, one that is hard to reconcile with the current assumption that it exists primarily to take in immigrants:

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.

Commenter Hundson writes:

America is not a propositional nation, America is a prepositional nation: “to ourselves and our posterity.”