We (the US) can be veritably fucked over if China starts to build weapons in space. Without all our satellites and stuff, it becomes infinitely easier to defeat the US in battle.
Yet, a high profile building of arms in space will undoubtably cause China to build weapons for their defense. Such is the problem of being number one and dealing with those who aren’t.
Perhaps we could build weapons secretly. Thus, if the US were to be attacked, an instant counter-attack could be mounted. This would completely surprise the enemy and result in… for lack of better words… total ownage. Maybe… But then what do we do afterwards?