I am living in a fairly touristic European town and have visited plenty of the main tourist towns across Europe over the last decade. Without any intention to be judgmental, I can safely say that in general, Americans and middle-aged Chinese tourist don't keep their voice down
intuitively. This is not their fault, of course. For example, both inner cities and living quarters are much more spacious in the US than in Europe, simply because the population density is much higher (117 per km² in the EU compared to 34 per km² in the US). In a typical European living quarter, if you are too loud on your porch or balcony, you are disturbing dozens of people or waking up babies. In the US, the next house may be so far away the neighbors won't even hear you. Add to this that around 77% of people in the US live in houses [0], compared to ~42% of Europeans who live in flats [1] (in countries like Switzerland or Germany, more than 60% of the population lives in flats, in Italy it's still over 50% [2]). In a flat, if you are too loud or if you don't walk quietly (especially in pre-WWII buildings), you are disturbing your neighbors. For that reason, in Europe (and I am sure in other parts of the world with similar population densities) children are reminded from an extremely early age that they have to keep their voice down and walk quietly when in a flat.
Again, I am not saying this applies to every American or Chinese, and of course there are German / British / French / Italian / Indian / Arabic / [...] tourists who do this.
[0] https://www.quora.com/What-percentage-of-the-American-popula...
[1] https://ec.europa.eu/eurostat/statistics-explained/index.php...
[2] https://en.wikipedia.org/wiki/Housing_in_Europe