Nice words from an idealistic point of view - but I am more a fan of poltiical realism, because in the end it is exactly that what drives most political decisions nowadays. Not human rights, nor other things like that, but always the same old stuff, namely maintaining and probably even expanding the own influence, getting and securing access to necessary ressources which are not in the own country, and maybe finding new trade partners to increase the own wealth.
Those are the driving forces behind most political decisions, nothing else. The so called "transatlantic partnership" never was one, it was always a lie, because partners are on equal terms, but in this "partnership" America always made crystal clear if needed who's the boss and who's the leud. And oh boy, if you tried to misbehave then, you were always for sure in for a rough treatment. And no other country in the 20th century was so busy with interfering and meddling on other countries' affairs than America; the Wikipedia list is huge.
And maybe the German government believed or still believes in this thing, I mean it's for sure easier and safer than to get an bigger army again, which always makes due to the history of the last two decades Germany's neighboring countries pretty nervous.
But the thing is: America at the moment is exactly doing what I described in the first paragraph. This has always been the driving force of all American foreign politics, sometimes nicely like an iron fist in a velvety glove, with Trump you just get an quite unobstructed view on their real intentions and goals. But the intentions have always been the same since decades, namely what I wrote in the first paragraph.
And why is that so? Because the politicians - doesn't matter if America, Japan, China, India, France, UK, Germany or whatever - fear to tell their fellow citizens the blank truth, that our lifestyle while nice, is unsustainable, and that in order to maintain it they have to fight either using diplomacy or using military options to sustain the current levels all of us do enjoy so much, and want to be able to experience forever so to speak.
George F. Keenan, who was one of the architects of the US foreign policy after WWII, wrote in memo PPS23 this about Asia back then:
"Furthermore, we have about 50% of the world's wealth but only 6.3% of its population. This disparity is particularly great as between ourselves and the peoples of Asia. In this situation, we cannot fail to be the object of envy and resentment. Our real task in the coming period is to devise a pattern of relationships which will permit us to maintain this position of disparity without positive detriment to our national security. To do so, we will have to dispense with all sentimentality and day-dreaming; and our attention will have to be concentrated everywhere on our immediate national objectives. We need not deceive ourselves that we can afford today the luxury of altruism and world-benefaction. "
In the end it comes down to this: America alone needs 40%+ of the worlds ressources to maintain its standard of living; China wants to have this way of living for its 1.3 billion something people as well, so some day they might up needing this share of the cake as well, and the same applies to India. And that's the problem: this standard of living in the long term is just not doable for these three countries alone, unless you have a second earth parked around somewhere in your trunk, more so if you put in Europe into the mix.
In reality most intelligent politicians do fear their own people, because they have no illusions whatsoever what might happen to them, if they are unable to maintain at least at a certain level the well accustomed living standard of their people without a suitable substitute: people with pitchforks going after them, riots, civil war, revolution. Take whichever scenario you like, you'll end up with some dead popular politicians. That's their justified fear.
So this is why the countries are behaving like they do; from an American perspective an European army like Macron suggested would mean that America would have much less influence on Europe, like it has at the moment. Having less influence on the EU means that the EU would become a much stronger competitor for global power, and a strong EU is something which is quite simple spoken not in the national interest of America, but goes strictly against it.
By the way the idea of an European army would have evolved regardless of Trump, just because due to the fact that the EU wants its own slice of the cake, and that Europeans interests are for sure many times not compatible with American interests. So in order to realize the own interests, the EU needs to have the proper tools at their own disposal so to speak.
Of course, Trump being who he is lacks the finesse and diplomacy to address this in nice, clouded ways. But even if someone more suited would be in the oval office, the goal and intentions would be for sure the same.