Others here have covered great points, especially that it is a physical loudness and presence.

I would add that everyone tends to be very knowledgeable about US culture, history, geography, politics etc from TV, films and news but with the “typical Americans” you are talking about, they know almost nothing about other countries or cultures. They might know very high level things like what Buckingham Palace is where the King lives but not much beyond that. The worst of the stereotype just don’t care and don’t show an interest in learning anything. It’s almost like a tick box to see certain things and then that’s their holiday done.

Slow an interest and curiosity and you’ll be fine. Look at what the locals are doing and try to copy them. If you go to London, everyone will stand on the right on escalators. Anybody with eyes can see that! Yet you’ll find so many people don’t look or care so get in the way.

Also, all countries have stereotypes that apply to most people but not everyone - the British are horrible binge drinkers who go for cheap beers in the sun. Im not like that but can certainly agree with the sentiment after seeing Brits abroad! Just sitting back and noticing goes a long way.

Shopping and service culture is very different. Most retail staff don’t have to welcome everyone, make small talk, fake an interest or have to stand up all day at a checkout to not be lazy. Restaurant staff often seem “rude” compared to America but in reality they’re just trying to do their job and we don’t always want the American style customer service. I’ll ask if I need help!