Regarding death rates between countries. A lot of it is down to what constitutes a Covid related death. In the UK, if someone dies within 28 days of a positive test then it is Covid related even if that person had a terminal illness. It is a very wide definition whereas other countries don’t always do the same.
Obviously there are many other factors such as population density, median age of population etc so there isn’t a huge amount to be taken from it. Other than advanced nations I would also say the statistics in most countries are fairly meaningless as they don’t have the resources to collect them.
Population density is a huge factor. It is why New Zealand could keep deaths to very low levels by sealing off their isolated country as there are few large population centres there and big gaps between those that exist. As they start to open up from restrictions things will still change but their natural advantage meant they were always going to cope better than most.
The UK is utterly different in every way. Far more people in much less space = very easy spread of a highly transmissable disease and things taking hold before you get chance to stop them.
The US has more people but spread over a much bigger area. The UK would fit into one state. This spread out nature of the population means it has an advantage over the UK - it buys some time - whilst still having the population density disadvantage over places like New Zealand.
In the UK it is not dfficult to work out why the biggest outbreaks have occurred in the past 18 months in the NW, Yorkshire and London. Density of population means fast spread. Meaning harder to stop by measures taken after it has started, Hence why the NW was in lockdown most of the time up to July. Possiblymore than in any western country and still has had lots of cases. It is the perfect breeding ground for Covid.
Look at the Isle of Man which had its own government and could isolate from the rest of the UK and did. It had very few cases luckily because it could not have handled them all and had to send patients to NW England if they needed real care.
But just as New Zealand will find in the end you have to open up and as soon as the IOM did things started to climb.
THey have for two years running now cancelled what is by a mile the biggest driver of the island economy - the TT races - because the vast influx of visitors from the mainland this would bring would almost certainly have overwhelmed their extremely small health service very fast indeed.
It is not usually because A did things badly and B did them well as to why cases and consequently deaths are high somewhere but not other places.
Covid is a disease that thrives in certain places and the densely packed island nation with huge concentrations of people in a climate that helps Covid no end makes the UK one of the easiest places to colonise.