"Propaganda" is a loaded word, but I would say that the Declaration of Independence was certainly a piece of rhetoric.
Huh...
So you feel that the US Declaration of Independence, OKA: The Charter of American Principles ... was language designed to have a persuasive or impressive effect on its audience, but often regarded as lacking in sincerity or meaningful content?
Well the King of England disagreed... as he sent the bulk of his Army and Navy to crush those who advanced it.
In terms of sincerity... The author and adherents to the US Charter of Principle closed with the pledge: "And for the support of this declaration, with a firm reliance on the protection of Divine Providence, we mutually pledge to each other our Lives, our Fortunes, and our sacred Honor."
A pledge which cost most of the signers, their health, lives and fortunes, along in many cases, their children and wives.
In terms of such representing MEANINGFUL... that would-be rhetoric recognized natural principles, to which the adherence to such has lead to extents of freedom and prosperity than any other rhetorical proclamation, in the history of humanity.
But given your relativist proclivities, there is truly no way that
you could have known that... proving once again, that as you so astutely noted:
THERE ARE NO LEFTIST AMERICANS!