I am not questioning the engineering prowess here. My point is what about RR makes it a strategic asset? Can the planes it supplies engines to fly on engines supplied by GE or Pratt&Whitney?
Toyota is a great company. I wouldn't call it a strategic asset of Japan.
Strategic Asset by its very definition means that it produces or offers something that is difficult if not impossible to replicate. Like Aramco is a strategic asset of Saudi Arabia. Like the Suez Canal is a strategic asset of Egypt. I don't believe RR falls into that category.
It is a strategic asset as it is only one of 3 titans in the field worldwide. They are so because of amount of IP and RnD they have locked up within them (and the borader network regarding this to other companies/sectors)....that allow them to do the full design + production of something like a jet engine from start to finish.
Similar to boeing/airbus being a duopoly (in mid/large commercial aircraft) and thus both are strategic assets too given the amount of IP and capital production locked up in them....and potential there going forward for the economies they involve.
Sometimes the aircraft, like you mention, has 2 choices or 3 choices for engines between the 3....but having a "1/3" say in it that is huge....i.e boeing or airbus have to design each of their aircraft with a specific engine or two in mind for them.....rather than say 10 - 20 (in which case those engine suppliers become far less strategic) in a more ideal competition environment.
Lot of time the military side is inertia spillover from the large dam of commercial side (and IP is often originated from the military projects first).....so all these 3 are involved there too....and of high significance again to being retained by the taxpayers/govts that funded them over 50 - 100 years etc.
If there were dozens of other companies in the field like in automotive sector (like you mention with Toyota), then sure they become less strategic. But it is the sheer size of these engines and aircraft that create this situation of 2 - 3 big guys....instead of dozens like in automotive since the engines, bodies, transmission etc etc are all far smaller and dont require the same intensity level of IP and capital machinery/processes (obviously just by looking at number of companies involved in the sector).
But instead of toyota in japan's case, think of the 1 - 2 specialist companies that make lithography machines for semiconductor fab....I believe the only companies in world that do them. They are not well known, but definitely strategic to Japan (and its why Japan can easily apply pressure on various semicon processes, which in turn was pressure coming from US to keep things supply chained in Taiwan on certain things.....rather than move more to China etc).
Your last sentence is correct, and thats exactly why RR is a strategic asset....as it is just 1 in 3 (and maybe 2 more if you go to safran, MTU but these guys are all partnered up with the big guys inevitably) in something of high-technology intensity too (where the natural market force would be to dissipate for more competition etc). That for sure shows its hard to replicate (or start new and grow to same size+expertise quickly etc) given the size of the sector.
With stuff like natural resources and logistics, that is somewhat different at that is more dictated by luck of the draw...rather than sustained RnD and capital effort....so they are strategic assets of a different kind.