I'll quote the summary from the essay. Parts I'll comment on later are marked with a *
"As numerous points of interest have arisen in the course of this essay, I close with a brief summary, to refresh the reader’s mind.
(a) We do not learn from history because our studies are brief and prejudiced.
(b) In a surprising manner, 250 years emerges as the average length of national greatness.
(c) This average has not varied for 3,000 years. Does it represent ten generations?
(d) The stages of the rise and fall of great nations seem to be:
The Age of Pioneers (outburst)
The Age of Conquests
The Age of Commerce
The Age of Affluence
The Age of Intellect The
Age of Decadence.
(e) Decadence is marked by:
Defensiveness
Pessimism
Materialism
Frivolity
An influx of foreigners*
The Welfare State*
A weakening of religion.
(f) Decadence is due to:
Too long a period of wealth and power
Selfishness
Love of money
The loss of a sense of duty.
(g) The life histories of great states are amazingly similar, and are due to internal factors.
(h) Their falls are diverse, because they are largely the result of external causes.
(i) History should be taught as the history of the human race, though of course with emphasis on the history of the student’s own country. "
The *s I'll talk about are decadence being marked by an influx of foreigners and the welfare state.
The essay itself talks about how immigrants don't really assimilate. "First, their basic human nature often differs from that of the original imperial stock. If the earlier imperial race was stubborn and slowmoving, the immigrants might come from more emotional races, thereby introducing cracks and schisms into the national policies, even if all were equally loyal". I think we can dismiss this argument.
"Second, while the nation is still affluent, all the diverse races may appear equally loyal. But in an acute emergency, the immigrants will often be less willing to sacrifice their lives and their property than will be the original descendants of the founder race." and "Third, the immigrants are liable to form communities of their own, protecting primarily their own interests, and only in the second degree that of the nation as a whole. " This is just from the "founder"'s perspective - you can just as easily argue that a "founder" will be less likely to sacefrifice their life and property for "an immigrant", and the "founders" are protecting primarily their own interests. What is it that causes division - the appearance of new immigrants who want to be treated just as any other citizen? Or that the "founders" do not extend full membership to immigrants?
* The Welfare State - the essay gives a lot of attention to welfare provided to the young and to the poor. Grants to university students, free medical care for the poor, etc. But I'd argue that the real problem with the welfare state isn't woth providing benefits to those who need it - it's the extension of those benefits to those that don't. University students shouldn't get free tuition (I don't believe) - especially as the people who benefit most will be the students themselves, through higher incomes, better opportunities at a fulfilling career, the networks generated at university that will help them succeed, etc. (They do need help financing, and I'm not saying gov't shouldn't pay some of their costs, just 100% of them)
But similarly, people who can afford to buy a house shouldn't get tax credits to help them buy a bigger one. People with a lot of assets (like the wealthy retired) shouldn't get free healthcare. Large corporate landowners don't need agricultural subsidies - but that's where the bulk of those subsidies go. Not to struggling farmers, but to the wealthy. When we talk about benefits and where to cut, the focus is generally on the poor - Medicaid, public housing, etc. But the benefits provided to middle class and wealthy people are much more expensive, much more entrenched, and much more damaging to the system.
Look at some of the other things that mark decadence as well - pessimism, defensiveness, materialism, frivolity. It's worth holding the mirror up when thinking about those symptoms.
On the anti-globalist view - you mention that you're too old and have seen the same thing over and over again, but maybe you're not old enough. Nationalism led to WW1 and WW2. The UN and the other global/regional institutions like the EU, the IMF, etc were set up in the wake of WW2 to provide a forum for the discussion of solutions so that a WW3 would not eventuate. I realise these institutions are not perfect, but they're less about building a world government that they are about developing an understanding between nations on how they can work together.