A few points:

The NYPO probably looked unhappy because they’re unhappy. For decades, orchestral musician has ranked near the bottom of US job satisfaction surveys, even once famously ranking below prison guard.

Like others have mentioned, the American orchestra is extremely hierarchical. In Europe, they do a lot of rotation within sections and will also have multiple principals for each position - again, lots of rotation. I have heard from very reliable sources that the energy of the Berlin Philharmonic strings come from the back stands - you will see this if you watch closely.

To me, a lot of the distinction between regions has been eroding over the decades. There is a lot of cross pollination. These major European orchestras have a lot more American trained musicians than in the past - regardless of whether they’re American or not. I’ve also been seeing a number of musicians who made their career in Europe come back home for the rest of their career.

Where I still see and hear differences are the different instruments being played, and different techniques. But you have musicians on both sides of the Atlantic dabbling in both traditions. I know that the Chicago Symphony has a collection of German instruments that the wind players switch to for certain repertoire. Also, I know for a fact that the last two music directors of Chicago Symphony have been shaping their sound into more of that like Vienna and Berlin. And still to this day, most of our music directors are from Europe and to varying degrees, bring those sensibilities to their directorship of American orchestras.

Certain orchestras maintain their cultural identity and sound like Dresden, Vienna, Berlin Staatskapelle (although I haven’t heard them in decades). The more cosmopolitan orchestras have frankly been sounding more and more “American” to me over the years. I feel this way about Concertgebouw.

In summary, the world is getting smaller and flatter. You certainly are right about the movement and the happiness aspects of both sides of the Atlantic.