I think in general America tends to have kind of a "supersized" version of everything. So in conversation Americans tend to trade anecdotes or quips or stories -- one story leads to another and the conversation is lively and entertaining -- there is little obsequious or even polite attention, and when it rears its head it smells oily and repulsive to most.
I think you nailed it with the competition aspect -- Americans are comfortable acknowledging a certain amount of competition, because American society tends to be more individualistic, so there is that bedrock understanding that of course there is competition, because we are all individuals living together in a society and competition is how you provide for yourself and distinguish yourself in contrast to the other members of your society.
Asian societies tend to be more communal, more collective -- and this leads to a quieter community, more hierarchical, more respectful -- but as you say, this is due to convention and custom, and masks true feelings. Thus it is a combination of a more tightly bound community and also a more controlled community.
One is not better than the other -- just different. Americans are boisterous and at the same time obnoxious. Individualistic and at the same time capable of more productive cooperation.
Reminds me of the WWII British saying:
"There's only 4 things the matter with these Yanks. They are over-ranked, overpaid, over-sexed, and over here!"