I think it would be news not only to me, but to CKC himself.
It was imperialism above all things that the older Chesterton found most anathematic. Indeed, he viewed it as the mortal enemy of patriotism, which was something by contrast that he held a lifelong and passionate affinity for.
In his essay ‘The Patriotic Idea’, Chesterton voices his disapproval not of patriotism but of the intelligentsia’s lack of rigour as well as their lack of values and passion:
‘Because the modern intellectuals who disapprove of patriotism do not [recognise the common needs of humanity], a strange coldness and unreality hangs about their love for men. If you ask them whether they love humanity, they will say, doubtless sincerely, that they do. But if you ask them touching any of the classes that go to make up humanity, you will find that they hate them all. They hate kings, they hate priests, they hate soldiers, they hate sailors, they distrust men of science, they denounce the middle classes, they despair of working men, but they adore humanity. Only they always speak of humanity as if it were a curious foreign nation. They are dividing themselves more and more from men to exalt the strange race of mankind. They are ceasing to be human in the effort to be humane.’
Here he is reminiscent, among others, of Dostoyevsky, who wrote (a little earlier in 1879) in The Brothers Karamazov: ‘The more I love humanity in general, the less I love man in particular.’ (Compare again Linus, who said, ‘I love mankind; it’s people I can’t stand.’)
In the same essay, Chesterton reasserts the position of the nation, contrasting its permanence with the transitory nature of empires:
‘[W]hen all the colonies of England have gone the wild way of the colonies of Spain, when some strange and sudden Waterloo has made the little dream of Beaconsfield (i.e. Disraeli) as mad as the great dream of Napoleon, something will remain, I am very certain, which matters more than all these levities. There will still be men who will die for England.’