Something to note about the UK, though, when compared to the US -- the British never really got a handle on their Delta surge.
Not to say that the US can thrown dirt on Delta just yet. But take a look at the top-of-the-mountain numbers. The US has about 4.88 times the population of the UK -- to make the math simpler, let's just call that "5 times larger".
Like the US, the UK enjoyed a period of COVID calm before Delta kicked in.
Going by seven-day averages, the UK's case counts fell below 10,000/day on 2/27/2021 and stayed there for almost four months, through 6/22/2021. Throughout almost all of April and May, they were below 3,000/day. Delta ramped up rapidly, very nearly quintupling their seven-day average between late June and July 21st when the UK reached their Delta high of 47,114.
The UK, however, never got on a true downslope with Delta. They had another Delta peak of over 38,000 on 9/9 and another pop above 47,000 on 10/23. At no point since their first Delta peak has the UK gotten south of 25,000 cases/day, and most of fall they've been well above 30,000/day.
So, how has the US fared comparatively through Delta? Treating the US as one singular entity can be a little dodgy since it's a huge place and different regions have had different Delta surges at different times. Still, you can get a sense that the US's baseline with Delta is a lot better than the UK's -- which is important because any Omicron surge is going to be laid on top of whatever Delta action is still going on.
Let's take that pre-Delta case number that marked the UK's pre-Delta lull, 10,000, and multiply it by 5 for the US. Applying that figure, the US had a briefer pre-Delta respite than the UK did -- not dipping below a seven-day average of 50,000 cases/day until 5/4/2021. The US drove the numbers down below 15,000/day for about a month -- early June to early July of this year. On 7/23/2021, the US's Delta surge had begun in earnest with the seven-day average rising back above 50,000 cases/day and staying that way ever since. The US's Delta seven-day average peak was reached on 9/2, 167,632/day.
The US's fall Delta
peak, then, was proportionally equivalent to the UK's fall Delta
baseline -- 167,632/day divided by five yields about 33,500/day.
Tying this into Omicron: It can be said that the UK is in a more vulnerable position than the US is with a new variant. Recognition of that vulnerability might be driving some of the more pessimistic Omicron press coming out of the UK.