Its quite true that the USAF is using Cope India to push for the F/A-22, Do read my posts I have given links for comparisons.
1. The AESA F-15's were "dropped" because of logistical concerns and because the IAF was not seen a threat meriting them.
2. The USAF was clearly overconfident.
They ,per their own admission, expected the Indians to be a bunch of Russia trained poorly equipped third world types..they were shocked to learn that IAF pilots flew upto 350 hrs per year...the Su30 pilots did exactly that.
3. They expected vintage aircraft and standard tactics- the IAF varied aircraft, changed tactics and mixed interceptors with strike packages to surprise the US..
4.If the US was not allowed the use the Amraams..then we also need to consider that the Indian aircraft were all inferior to the F-15's. The F15's had the APG63 radar...the best the Indians fielded was the NOO1V on their Su30K's...a generation older and equipped with a cassegrain antenna.
5. The training matters...Indian pilots fly blue air...they train against the best of their peers..the USAF flies red air..per their own subsequent admissions and sometimes that leads to a policy wherein the opfor has downgraded to simulate realism..and training is easier. The IAF system is more brutal and hence has its payoffs.
6. The USAF AMRAAM limitation sucked but then so did the fact- for the IAF- that their avionics werent as good. The IAF did not field their Su30MKI's which could easily match the F15C's.
7. Out of the 12 a/c- half of them were strikers, not air to air aircraft. The USAF F15C's faced approximately equal number of Air to air opponents, each of which was flying an inferior aircraft overall. (As US percieves)
8. The IAF MIg21's are the upgraded versions in service- they have Russian radars, avionics, Indian RWR's and Israeli jammers..plus R77's, helmet sights and R73E's. In the close fight and with an element of suprise they can level the playing field.
9. Indian Sukhois used their IRST's to conduct passive attacks against the F15's taking them by surprise. Again- tactics backed by technology.
In essence, Cope India was "dont underestimate your opponent"- if you do so, you get yourself surprised.
Thats exactly why the IAF was invited to the Alaska exercises thereafter..they proved their worth as credible opponents and hence the USAF wanted to see if they could spring any more tricks.
The USAF used the exercise to push for the F/A-22 but the F15 jocks were caught off guard and that led to some widespread derision in the competitive fighter jock community.