People actually speaking of nationalism - as it is used in politics - like it's a good thing.
Trump's kind of false patriotism is at best a wakeup call and a 'privileged bragging survival of the fittest' policy where the market rules all. Our European versions (Le Pen, UKIP, Wilders, Sweden Democrats etc) are (and only because we're economically too small individually to be anything else) nothing but racist, classist and fascist.
This is not an issue we can afford to throw away protest-votes on - if you vote for Le Pen because you're sick of the established elite of corrupted politicians, you are supporting not only what is the official party manifest but also the entire ugly underbelly of a society we all live in and have spent a century trying to make better. And since, unlike the US, most European countries do have more than two political parties, surely you can find something better than that.
Despite ALL the flaws of the European Union, its member states, the human species in general, giving in to the dark side should not be an option.
The world wasn't better in the old days - we had as many wars as we do now, we had as much crime as we do now, children were as likely to bully other kids as they are now. The only difference is that we're more aware, that people's rights are more protected, that we have developed a mindset that protests and doesn't just accept what the upstairs tell us to do.
In so many ways, the world is a better place now - and a lot of it has to do with cooperation, with actively working together for something that's not just in your immediate interest or mine, but can possibly benefit the world beyond our scope.
The EU, the market, society as a whole - we are all not only part of these, but they literally wouldn't exist without us and there are civilised, democratic ways of changing something for the better without destroying it. (Which is kind of not so funny considering how these people are so against leftist revolutions, or anti-system parties when Trump literally went to war with slogans like that. And Spanish Partido Popular calling Podemos populist and anti-system, as if it's an insult. Because obviously Podemos are populist and anti-system; they are a party consisting of ordinary people turned politicians, because the current system is doing a better job at protecting the banks and businesses than the people they're always claiming to work for - and paying themselves handsomely for it too.)
If you - with or without all your best intentions - vote to bring down the European Union; if you as a European or as a human, support Trump's business model, you are doing nothing but playing into the hands of the money-making market and its rulers. You're supporting the same system that covered the Spanish coastline with hotels and adjacent parks that consist of raked gravel paths and a line of palm trees that give no shade, and bungalows with empty terraces and paved gardens "because the tourists come here for the sun and cheap wine"; you are supporting a view of the world where it's every man for himself - and I do mean every man, because there is no way to excuse or explain away such misogynistic attitudes and views. This is no longer the usual budget discussions and compromises, where you can accept some losses in one area for the sake of something more important right now, in another. Trump and the far right are so ugly that you cannot pick out the (rotten) raisins and not swallow the big fat flies with them.
Not everybody can nor wants to stand on the barricades, but people before us did just that to give us the right to make our voices heard. So, if you really do have fascistic, racist or in general non-inclusive tendencies, or are willing to support such a world view, fine, go ahead, but for the rest of us, vote consciously, do not take it lightly. Make a decision as educated as you can, and really really think about what you're doing.
Don't be selfish.
Try to not be too short-sighted.
In short, just try.