These World War II advertisements to bolster those on the Home Front have been pretty trendy for awhile now (courtesy of Keep-Calm Ltd), and note that they were part of the English war effort.
Now consider this American bit of advertising:
Nothing subtle about it. But I do love the simple message: Burning gas supports the enemy. Bill Mahler thinks so too:
Unfortunately, telling Americans today that it's essentially un-American to do a distinctly American thing--driving alone--would likely never fly with major industry, and certainly not the government. Might make a good bumper sticker, though.