What is greater utility per supercomputer exactly?
I'm more inclined to think you are specifically trying to confuse the issue to make it look like the Chinese supercomputers are somehow inferior to the American ones. The capacity of supercomputers is measured by the Linpack benchmark suite which is the same test suite used in every case. In other words, it is pretty objective test measuring real task performance, and if some supercomputer scores higher in this test, it can be said that it will be faster than the rest of the pack in the majority of tasks that such machines are mostly used for
Utility refers to the harnessing of all available cores.
Let's say China has 1,000 cores and the USA has 500 cores. If China used every core every second of the day for one year straight, it's utility would be 365,000 core-days per year, maximum. With half as many cores, the USA max would be half of that, or 182,500 core-days per year.
Suppose both countries consumed 150,000 core-days of processing in a year. Which country would have the greater utilization?
The USA would since it used a higher percentage of its supercomputers resources.
Most supercomputers have cores that sit idle for weeks at a time. It is very hard to keep them all busy.