Conveniently, since we're all having ANOTHER row about whether you can be left-wing and patriotic, I wrote about it almost exactly a year ago the last time we had the exact same row! https://unherd.com/thepost/can-patriotism-be-progressive/

my basic diagnosis – ripped off, as so many of my insights are, from @slatestarcodex – was that the basic trouble is that most liberal-lefties (inc. me) basically *don't* feel much attachment to their country, which is fine, but which makes it hard to display it convincingly

("most" may be overstating it. Many?)

And it's a problem because most voters DO feel that attachment, so you either have to just not pull that lever or pull it in unconvincing ways (eg Rebecca LB, "I'm proud of Britain because of, uh, a Lancastrian millworkers' strike in 1862")