I see two major things here:
A) I'm German too, we have made very bad experiences with nationalism and patriotism. In two world wars it ended up not only committing atrocities against others, but also resulting in disaster to ourselves. Our state's legacy is anti-fascist and anti whatever the nazis stood for, which involves being very cautious about nationalism. Americans have a very different experience, they're used to be on the winning side. Even if they lost in Vietnam, that didn't mean disaster at home. American democracy has lasted for more than two centuries--their historic main antagonist, the Soviet Union, lasted some 70 years.
To this day, the USA is dominating culturally and economically. In the internet age, well, Microsoft, Google, Apple, Facebook, Twitter... they're all American companies. Telling people that the American way is the best way is an easy sell.
B) consider the sheer size of the USA. The only country in the world that is significantly larger is Russia. It spans 4 time zones, and you can travel 4,000 km and you're still in the USA. Its area is more than twice that of the European Union. Which all means that Europeans are more likely to have visited another country than Americans do, more likely to have been exposed to different ways. Americans are more likely to never have visited another country, and not having experienced different ways. Not knowing different ways is a major factor in favouring your own.
And while I'm talking about all this, I want to stress that we aren't free of it at all. We Germans still have a superiority complex, even if we don't display it openly. From my experience as a salesman, I can tell many stories about how we trust German design and German quality and are wary of anything, say, from Italia--I could talk all I wanted about how that Italian company's products are actually better than any of its German competitors, but it would fall on deaf ears. People think German products are best, and many German companies with inferior products prey on this belief.
When minimum wage was discussed in Germany, it was all about how it would theoretically impact (or ruin) German economy. Nobody ever considered looking at the many other EU countries that already had a minimum wage, because... well that would mean Germany could learn from other countries and that would be a silly idea, wouldn't it?