I feel so goddamned naïve for thinking Bush Jr. was the worst president we'd ever have. Yes, The Shrub led us into an unjust war. Trump has frittered away the bulk of soft power the USA has enjoyed since WW II, essentially committing us to reintroducing War just to show our intent and will.
I'm not sure if Trump had anything to do with it to be honest. The reason the US 'lost' power is because China is the first worthy rival to US power in decades.
When Sadddam promised the mother of all tank battles and had his Cold War era tank army demolished by high-tech cruise missiles the US and by extension NATO were at the 'height' of their power.
People have mistaken the reluctance of the Russian Federation to intervene up until the mid 2000's with 'acceptance' of the current security situation.
The Russians simply couldn't do anything to stop the US from attacking Serbia because they had a mostly obsolete army like Saddam.
Once they had modernized their armed forces and were able to strike back and win (in places like Georgia and Syria), they started doing so.
Meanwhile the US policy was that the 'cold war' was over (Obama famously told Romney this in a debate) and the Russians and Chinese were 'partners' on the global stage even though there was no commitment from their side.
That's the reason US power waned, there's no longer a clear technological advantage and the loss in Afghanistan has confirmed the view that the US can no longer dictate their will without an army in place.
The other reason is the US barked up the wrong tree with Iraq. All those resources could've been spend on containing China (and even Russia) and propping up China's asian neighbours.
Condoleezza Rice I believe actually admitted this to Bush, making the case that the US should've invaded to free North Korea instead of Iraq.
At the same time Europe has realized after 2 'lost decades' that their foreign policy of just following the US and leaning on their army is not the best way to go about things.
It seems to me that short of waging more wars with millions of dead (i.e. what Trump didn't want to do in Afghanistan) to keep their enemies at bay there is little the US could've done to prevent losing their soft power which was based on a short lived military, economical and technological advantage.
In the end it was Obama who told the world the US would 'lead from behind' essentially doing nothing to protect US puppet rulers in Egypt and elsewhere while at the same time supporting a coup in Russia's backyard that the EU was very uncomfortable with.
And George H.W. Bush and Bill Clinton squandered the opportunities to pull Russia into NATO and Europe and instead let it spin out of control which soured Russians once yearning for freedom on the ideals of Democracy.