This is not true.

It is what is called “skinny fat“.

If you are skinny fat you still have noticeable abdominal fat. You might not see it when somebody has a t-shirt on but it's still very obvious

To put this another way skinny fat just means you are not overweight but you have a high body fat percentage (eg lacking lean mass). So while you might not look like the average American there will still be significant visible abdominal fat, likely love handles, etc