Leaving a significant tip (15-20%) for service in restaurants and other service industries is standard in the U.S., whereas in many countries, tipping is not customary or is much smaller.
Serving and consuming large portion sizes in meals, especially in restaurants, is common in America but can be surprising to those from countries with smaller portions.
Automatically filling drinks with lots of ice, even in cold weather, is a typical practice in the U.S., but not common in many other countries.
The widespread and prominent display of the national flag at homes, businesses, and public places is much more prevalent in the U.S. than in many other countries.
In the U.S., the price displayed on items often doesn't include sales tax, which is added at the register, unlike in many countries where the displayed price is final.
Striking up conversations with strangers or sharing personal information quickly can be seen as overly friendly or invasive in more reserved cultures.
Having many stores and services available 24 hours a day, seven days a week, is common in the U.S., but rare in many other parts of the world where there are stricter hours of operation.
Utilizing drive-thrus not just for fast food, but also for banks, pharmacies, and even weddings, is a uniquely American convenience.