Many of the factors responsible for the fading of US military dominance are directly attributable to US actions and policy. From Federico Pieraccini at strategic-culture.org:
Starting from the presidency of George W. Bush to that of Trump, the U.S. has made some missteps that not only reduce its influence in strategic regions of the world but also its ability to project power and thus impose its will on those unwilling to genuflect appropriately.
Some examples from the recent past will suffice to show how a series of strategic errors have only accelerated the U.S.’s hegemonic decline.
ABM + INF = Hypersonic Supremacy
The decision to invade Afghanistan following the events of September 11, 2001, while declaring an “axis of evil” to be confronted that included nuclear-armed North Korea and budding regional hegemon Iran, can be said to be the reason for many of the most significant strategic problems besetting the U.S..
The U.S. often prefers to disguise its medium- to long-term objectives by focusing on supposedly more immediate and short-term threats. Thus, the U.S.’s withdrawal from the Anti-Ballistic Missile Treaty (ABM Treaty) and its deployment of the Aegis Combat System (both sea- and land-based) as part of the NATO missile defense system, was explained as being for the purposes of defending European allies from the threat of Iranian ballistic missiles. This argument held little water as the Iranians had neither the capability nor intent to launch such missiles.