The US is strong because it wields its power effectively. It puts down its enemies economically, it puts down its threats with overwhelming violence, and it props up allies where needed. This maintains its status, ensures that nobody can act against it except for show, and guarantees further economic prosperity. The US has a strong economy because it maintains a presence with each of its trade partners. Some of that is through treaties with larger allies, some of that is through base agreements with smaller allies, and some of that comes in the form of missile strikes and occupation to remind the less friendly nations why they need to fall in line and keep things amicable.