Americans actually began celebrating July 4th as an official national holiday only after Franklin Delano Roosevelt made it so in 1941.
In his radio address to the nation on July 4 of that year, FDR acknowledged a worldwide threat to civilization and to democracy, the American democracy included. His remarks were clearly meant to prepare Americans for entry into WWII, an idea that was not popular at that time. FDR stood on American principles and not on political convenience.
Here are some excerpts from the radio address:
“In 1776, on the Fourth day of July, the representatives of the several States in Congress assembled, declaring our independence, asserted that a decent respect for the opinion of mankind required that they should declare the reasons for their action. In this new crisis, we have a like duty.
“In 1776 we waged war in behalf of the great principle that government should derive its just powers from the consent of the governed. In other words, representation chosen in free election. In the century and a half that followed, this cause of human freedom swept across the world.