Do Americans say ground floor?
In American English, the floor which is level with the ground is called the first floor, the floor above it is the second floor, and so on.
In British English the floor at street level is called the ground floor, whereas in American English this is the first floor.
The floor on ground level is called the Ground Floor, because it's on the ground. Every floor above that has a number. The 1st floor above the Ground is the first floor, the 2nd floor above the ground is the 2nd floor, and so on. This is not a uniquely English phenomenon, the same applies in most of Europe.
Normally, the floor is what you walk on inside a building, and the ground is what you walk on outside. I too find it jarring to hear the words “floor” and “ground” used interchangeably. But many people do this. Not only do they refer to the floor as the ground, but they call the ground the floor.
Because, in the US, the ground floor is the first floor you come to. It's the first floor in the building, not the zeroth floor. Other countries consider the first floor as the first floor above street level.
Answer: Back in the era of kings and queens, the floors of a castle were used for storage during sieges. Each floor would be used to store various different items, including weapons and food. The floors were referred to as 'storeys'.
In the United States, the first floor and ground floor are usually equivalent, being at ground level, and may also be called the "lobby" or "main floor" to indicate the entrance to the building.
In British English, the floor of a building which is level with the ground is called the ground floor. The floor above it is called the first floor, the floor above that is the second floor, and so on.
In Britain and most of Europe, the ground level floors are called the "ground floor", the next level is called the "first floor". In most of the United States, Russia and China, the floor at ground level is called the "first floor", the next level is called the "second floor".
US : the floor just above the lowest floor. British : the floor that is two floors above the ground floor level.
What is the American word for first floor?
In North American English the floor at street level is usually called the first floor, the one above it is the second floor and the one below it is the basement. In public buildings the floor at street level can also be called the ground floor.
In the United States, Canada, Australia, and New Zealand, the first floor is the ground-level floor. One doesn't have to walk up stairs to get there. The floor above the ground-level floor is the second floor.

In the United States, the first floor and ground floor are usually equivalent, being at ground level, and may also be called the "lobby" or "main floor" to indicate the entrance to the building.
In Britain and most of Europe, the ground level floors are called the "ground floor", the next level is called the "first floor". In most of the United States, Russia and China, the floor at ground level is called the "first floor", the next level is called the "second floor".
In the United States, Canada, Australia, and New Zealand, the first floor is the ground-level floor. One doesn't have to walk up stairs to get there. The floor above the ground-level floor is the second floor.
In North American English the floor at street level is usually called the first floor, the one above it is the second floor and the one below it is the basement. In public buildings the floor at street level can also be called the ground floor.