It's certainly true that many Americans get very jingoist about their so called "patriotism", but as others have pointed out, most Americans aren't like that.
I think the international community supposes that Americans are over-patriotic because of the massive support for the Iraqi war. True, the Bush administration unintentionaly tried their darndest to make us look like bufoons in the international community, and the Fox News channel is America's highest rated cable "news" network despite the network never pretending to ever be an objective news source, however, the overall support for the war has little to do with silly nationalism.
The US support for the war is pretty simple; most US people believe that Saddam Hussein either had a direct link to the 9/11 attacks, or that Saddam Hussein has a large stokepile of WMD that could be used against the US, or was dangerously close to it. An even smaller minority believes that liberating Iraq is a great idea all in itself. So while most may not vote to re-elect Bush, or most may be well feel that Bush will exploit Iraqi resources after the war, the very fact that the security of US citizens was believed to be at risk, was itself the sole or primary reason for supporting the war (if this premise were indeed proven/ strongly hinted at with good evidence, I too would have supported the war and not be a "Bushman" as well.).
The protest against anti war protest is due to other factors, IMO. In the US, people on the far right tend to demonize people of the center left (most Democrats), left (some Democrats) or far left position (green party,etc.), as being "unAmerican" in general, anyway. So this disposition is simply a continuation of a rather insidious habit that was already there. Since virtually all radio, and now increasinly more TV is controlled by right to far right ideologes, this idea can gain easy access through that outlet, and with most Americans accepting that Iraq really is a threat to US security, people will necessarily be a little pissed at anti war people who appear to not care about the country's national security.
What I find kind of ironic is that my hometown of NYC, the city most affected by 9/11, is one of the more anti- war cities in America. The city council passed a resolution condemning Pres. Bush's war without much fanfare, and even in the midst of war, less than 50% of New Yorkers supported the war (at least in NYC). So I haven't had to hear too much pro war dogma locally, but I've certainly come across a few people of that bent, nontheless.
