I can happily go point by point here, but my original comment wasn't intended to suggest I agreed with the current state of world military balance and shouldn't be taken as implicit support of US policy.
That said -
* The S-400 is an impressive system. The Russians have so built ~300 of them, and like any system, the soft factors are more important than the paper facts suggest. Training, deployment, doctrine, and strategic/tactical goals would greatly affect the viability of it on any modern battlefield.
* Space Superiority is more than just ASAT capabilities, but its an area that few other countries have ever even attempted, and with the US's dominance in rocket technology (arguably anyway) and high altitude laser platforms, I'm fairly confident it would be a stalemate at best, with even the closest competitor. I would agree its an area of US defense that will need special attention over the next ~10 years.
* Insurgency =/= Great War.
* OIF was heavily supported by carrier based aircraft, and there are exactly zero countries that posses a modern enough navel force to threaten US control of the actual blue water areas. US Submarine technology is decades ahead of everyone else at this point. There are concern developments in this area, but again, we're talking "Great War"
* True point. Wars tend to get people pointed in the same direction though. Especially "Great Wars"
* US pilots put in more seat time than every other country combined. This is a factor that cannot be overstated. Putting 10x the number of the worlds best plane in the air means nothing if the actual operator cannot leverage those tools effectively.
In the end, these are all great points as to why the US has room to improve its lead, but none of them really address the core point which is that the US is currently the undisputed leader in almost every military category, and any "Great War" involving the US would be a very lopsided affair. You're more than welcome to pick your challenger and we can see how long it takes me to make a list twice as long with their problems, although I can't guarantee I'll actually spend the time doing that today :)