Science fiction has long explored the idea of humanity employing some kind of space force. Control of, or defence of space, depending on your viewpoint, is always going to be important. Although the name ‘space force‘ refers primarily to the US agency bearing that name, the idea is far older. There is significant scope for exploring stories relating to the space force, both as hard science fiction or soft.
Brainstorming
Perhaps you do not think that the United States should be in space at all? Perhaps you feel that any space force should be under the control of another nation? Maybe your preference would be for control to be placed in the hands of an internal coalition or other organization. Could the United Nations be the best organization for this role?
sythesising ideas
Whatever you decide, perhaps including all of those viewpoints would make for an interesting background for your story. Perhaps a nationalistic antagonist could oppose your internationalist protagonist or vice versa. Could an individual nation take overall control of space and control who could develop space through a planetary blockade? Your final resolution could show all combatants coming together and overcoming their differences, providing a happy ending. Alternatively, you could show those differences as irreconcilable and provide a downbeat ending.
genres and resolutions
The space force story idea is particularly suited to near future or alternative history science fiction ideas. As a new branch of the military, few will be truly familiar with how it operates, and even if they are, those methods and procedures will probably change as the organization goes through changes. Few people like change, and so another idea might revolve around how the ‘old guard’ in previous forces (Army, Navy, Air Force) try to undermine the fledgling service. Alternatively, the new force could distinguish itself by excelling in a real-world conflict which could change the views of those initially opposed to it.
In all of these variants, I have tried to show a conflict and suggest options for a proposed resolution. None of these suggestions should be taken too seriously. This is your story and I am just trying to trigger a few story ideas for you to develop.