Not necessarily, I’m American and quite softspoken in public. In fact, people other than the ones I’ve known the longest, and sometimes even those, often have to make me repeat myself. I am half Japanese, if that matters. My mother (full-j) is fairly quiet too, though she can certainly laugh and yell loudly. I’d say a higher percentage of Brits I’ve talked to have been quiet, but a few were really loud and annoying (I recognize this as an individual thing, though). The few Irish and Australian people I’ve been in conversation with have seemed a little louder than normal (or just more assertive with their sentences, maybe).
I’m an American who lives abroad and I can state without hesitation that Americans can be very loud in public (Australians and Germans too). It’s always kind of jarring when I go back to the states and people are just shouting conversations to each other in public, like one family member is in the next aisle of the supermarked and the mom is asking what kind of soup he wants.
Why is it when Americans are loud, it’s a bad thing, but when those from ther cultures are loud, it’s considered a good thing - their loudness is given positive labels such as expressive, animated, gregarious, and so on, or just accepted as part of the vocal timber of their native language, rather than considered “obnoxious” as Americans are?
Americans and Australians live in spacious countries and have expansive, individualistic personalities; Germans are just imperious order-givers. 
Germans also do that weird thing where they mark their spot by the pool at five AM then go back to bed and expect everyone to respect their claim (but that’s another thread).
I’ve just returned from a vacation in Japan and noticed that the loudest people around seemed to be the Americans, which made them stand out rather often (“TRY THIS PIECE OF SUSHI, MOM!!!”). Then again, I traveled alone, so I didn’t have anybody to shout at in German. I noticed a couple of French tourists, though, who quietly talked amongst themselves.
However, I went to a concert at the Tokyo Dome, and let me tell you, there’s nothing more deafening than about 55.000 Japanese teenage girls when Japanese idols come on stage.
Yep.
I think there’s a pretty stark disconnect between urban Americans and rural Americans. City dwellers, especially those in the East, tend to raise their voices a lot. To us Chicagoans, no quiet lot I assure you, a New Yorker, Bostonian, or New Jerseyite is extremely loud and obnoxious. Then again, you plant one of us out in Kentucky or New Mexico and we’d be the loudmouths.
I’m guessing that there’s a pretty heavy bias towards Eastern Urban Americans doing more international traveling than your average rural/suburban Midwesterners and Southerners. As a result a European is much, much more likely to meet a New Englander and their loud city accents versus a more nominal sounding Hoosier.
:dubious: Have you been buying food from the Paisleys?
I’ll accept (perhaps) the speech accelerator, but hardly the megaphone. When anyone English passes me by in Belfast, I always think to myself “And you guys think the Americans are loud?”
Anglophone Cameroonians can beat Americans in a loudness match any day.
I think loudness is related to how open and expressive your culture is.
Again, though, I’ll say this: why is loudness considered a bad thing when Americans do it, but a good thing when it’s other cultures?
Where in this thread is it suggested that when Americans talk loudly, it is a bad thing, and the opposite when it’s non-Americans?
A point I’m not sure I made in the OP was that these people were discussing somewhat intimate facets of their lives. It wasn’t just small talk.