"In America" indicates that something happens within the United States. Sometimes it broadly means anywhere in the Americas, depending on context. It frames location, culture, laws, or norms when comparing places or practices.
In America the President reigns for four years, and Journalism governs forever and ever. Oscar Wilde
There are some circles in America where it seems to be more socially acceptable to carry a hand-gun than a packet of cigarettes. Katharine Whitehorn
Eighty percent of married men cheat in America. The rest cheat in Europe. Jackie Mason
All great change in America begins at the dinner table. Ronald Reagan
In America nothing dies easier than tradition. Russell Baker
In America half an hour is forty minutes. German Proverb