Scorpion already gave you the answer:
"latest and best equipement", wich means that the F/A-22A, the F-15C/D, the F-16C/D, the F/A-18E/F and the F-35A/B/C have a very good performance. And F/A-22A, F/A-18E/F and F-35 are clearly the latest developments, do you agree, AirMarshal?
"overpower" is the best reason, why the US have the best airforce (Airforce, Navy and USMC combined): They simply have quite a lot of good fighters (more than any other country). You can take Singapore as an example. They have a very good equipement (approx. 60 F-16C/D and 40-50 F-5S). That's a very good airforce for a county of that size and a good airforce for this region, but it can't compete with the USAF(because of it's size).