Dave,

We can certainly view the world from two different views that often an ocean apart it seems.

There have been periods in recent history where - mainly the liberal democracies - have been at a minimum puzzled and many have strongly opposed what the USA has pursued. Vietnam comes to mind, then the arrival of President Reagan, with what appeared to be dangerous policies, Star Wars and cruise missiles came to the fore, in Europe.
I don't think liberal democracies were at all opposed to our intervention in Vietnam initially. In fact, it was the French who prodded us to get involved. As the war dragged on, and more importantly it was televised and propaganda-sized popular support ebbed. Nonetheless, liberal democracy was threatened by communism, and for a number of reasons that were both right and wrong in hindsight, the U.S. decided to make a stand in Vietnam.

With the declared end of the 'Cold War' there was a shared perception it was a new world and a diminishing public interest in national security.
True, but also true after WWI, and for a short period after WWII. Understandably, everyone wants a peace dividend.

9/11 meant the USA had global sympathy, which has slowly ebbed as the 'Long War' has lengthened and the public has got nervous, even fearful of what may come. I doubt there is much public support within the "willing coalition" to commit blood and gold to Afghanistan.
I think you're right, sympathy has a shelf life, and ours is expiring. Powell's intent of short and decisive wars was a worthwhile aim, even if unrealistic in practice. The character, political purpose, and world evolves too much when we wage long wars, and this change generally undermines both domestic and international support for these wars. However, unlike Vietnam, continued atrocities conducted by terrorists sustains enough support for our efforts in Iraq and Afghanistan to continue in much of the liberal world.

There has always been a concern, maybe a fear, that the USA would simply 'put America first' and not be too worried about the national interests of allies, friends and others. President Trump has accentuated that.
The reality is all countries look after their national interests first, but few other countries have the impact on global security that U.S. security decisions will make. Overall, I think the U.S. have been good, not perfect, stewards of the international order since the end of WWII.

One consequence, alongside many other factors, can be seen in the UK where a politician once regarded as on the fringe is now the Labour Party's leader and who historically has not been friendly towards the USA.
Slamming the U.S. is currently popular, largely due to President Trump's admittedly problematic communication style. However, if Europe could move past its excessive political correctness and evaluate the Clinton compared to Trump, I think they will find Trump is the better deal. Clinton's support for intervention is at least partly responsible for the refugee crisis Europe is wrestling with now. President Trump says dumb things in rude ways, but on the other hand he has surrounded himself with a competent national security team.

I would ask two questions in response: Does the USA listen to those who are allies and friends? Can they really have an impact today?
Yes, our leaders listen. Often those discussions are not held in public, and deals are made, despite public political rhetoric saying something different. Allies and friends can and do make an impact. Keep in mind, the U.S.A. is much less likely to bury its head in the sand compared to other liberal democracies when there is a security challenge on the world stage. It often seems many of our allies and friends believe if we simply ignore a problem it will go away. Hitler benefited from that liberal mindset.