The end of post-ww2 American hegemony is a bad thing. We've lived in a world of unprecedented peace and prosperity. That is looking like it's over now as we bully and discard our closest allies and empower our natural enemies, tearing apart the world order. It will be non-trivial to rebuild trust and cooperation going forward.
Good luck, EU.
For Europe, the point when we started to relax and just coast was after the fall of the Berlin wall. Before that, the spending of European allied countries was relatively high.
For a while it really seemed like we would finally had peace in the continent.
And Europe has benefited a lot from the peace dividends that came after the fall of the USSR.
Sadly those times are over and it's clear that Russia is back in to their old imperialism mantra.
When we look at individual European countries, it's obvious that it does not match the USA. Not in population, GDP, military, etc. But as a "United States of Europe", it's much closer on all metrics.
What is more concerning is that if the USA continue to distance from their European allies, several of them will start to consider developing their own nuclear weapons.
In the EU, only France and the UK have nuclear weapons. Germany hosts American nuclear weapons. But if the USA splits from the EU alliance, then Germany will make their own.
Poland in previous years have told the USA that they want to host nuclear weapons, because they saw the return of Russian imperialism, and they have a long history of suffering under it.
Once again, if the USA abandons the its's EU allies, then Poland will create their own.
And a similar thing will happen with other countries, such as Japan and Taiwan. Israel, supposedly, already have their own.
But what this means is that there will be a nuclear proliferation. One of the advantages of the Pax Americana was the limited proliferation of nuclear powers.
And when there are many more countries with nuclear weapons, there are more fail points, for a nuke to be used in anger.
One thing is what several US presidents have been doing, pushing the EU to increase their military budgets.
A whole different thing is what Trump is doing, by alienating the USA's oldest and most reliable patterners. This is neither good for the EU, nor for the USA.
And if the USA allows Ukraine to fall to Russia, a lot of current allied countries will see the USA as an unreliable partner.
This means nobody will trust the USA to mediate a peace deal in any future situation.
A situation, like that of a US President negotiating the peace deal in Northern Ireland, will never happen again, because nobody will trust the US again.
And this is bad for everyone, except dictatorships like Russia and China, that thrive in a world of suspicion and mistrust.
