Preface: As a patriotic American, I'll be filtering my answers through that lens. Different nations have different national ideals, I'm not going to assume that they are always the same as ours. So these answers can easily be different for those in other nations.
Love for one's nation and national ideals. Hence, keeping to the Constitution, respect for life, liberty, and the pursuit of happiness (especially including private property), respect for laws which protect them, and being a land of opportunity for those who legally come here. I believe this is good.
I believe they are. Since I believe the aforementioned national ideals are good, I don't see a problem with American nationalism. Keeping to all of those won't do intentional harm to good people.
Ah. The media. The starkest examples of media impact to me are what happened in the months following the September 11, 2001 attacks. It seemed as though many in the media (which reflected a trend in the general populace, and fed into it) were rediscovering their patriotism after that. And with rediscovery can also come silly overcompensation for not having "enough" of it before. Some of it was kind of chuckle-worthy, if not for the fact that almost all Americans were hurting in some way over it. By the way, that's when we started seeing the military tributes at almost every high-profile sporting event.
Whenever it's an especially patriotic time - i.e. Memorial Day, 4th of July, etc, you see products being pedaled to take advantage of that. They have ranged from "meh" to rant-inducing.
Lots of people are divided in the US, but patriotism itself provides common ground for lots of different people who would otherwise have nothing to do with each other. I'm not including anti-immigrant rhetoric in this, because that's not patriotism to me. That's fools thinking they're being patriotic.
I expect that everyone who plays on the world stage is a patriot to whichever country they represent. They are paid by their governments to put their own countries first, and deal with other countries - either peaceably or aggressively - in a way that furthers their own country's best interests, or at least what their governments think their best interests are. All the more reason why our diplomats and leaders should be patriotic.