Having lived in Australia and the UK as well as driven a motorcycle 20000km around Europe and a car from LA to Miami I feel that I can comment without the citation.
Germany have the best drivers as they have the highest standard of awareness of other drivers on the road and they are very consistent in what they do. The behaviour on their autobahns and highways is completely predictable. The UK you need to learn what is the etiquette in order to be comfortable. They drive faster than their continental cousins on the same grade road, they tend to follow closer and generally require a lower gap. That said they are acutely aware of every other car on the road. They can do the zip merge and will let people in but if you are not from the uk you will find the spaces small.
America tends to be the opposite end of the spectrum to the UK. Technically I am sure their driving skills are find but awareness of others on the road appears to be zero. Keeping to the slow lane also seems to be an unknown art. Also on smaller streets stop signs and the like seem to be on a do I feel like following this today setup. If you are merging onto a highway you can pretty much bet the cars on the highway won't speed up or slow down to make life easier for you.
Australia sits half way between the UK and USA. There is slightly more awareness of other drivers (but not enough) people will accept a smaller gap and are more consistent drivers. Running stop signs and traffic lights is a big no no in Australia and most people don't do it.