We need the F22 for a few reasons. First is that every major nation in the world has purchase orders in for fighters that are a generation newer than our F-15s and F-16s. That puts us at a definate disadvantage. F-15's can be upgraded to a certain extent, but they will never be even remotely stealthy. Which brings us to the next reason. New SAM technology has advanced to the point where the aerial battlefield is no longer survivable. New Russian designed SAM systems are not only designed to shoot down aircraft at ranges up to 200+ miles, but they are also designed to actually engage and shoot down any weapons aimed at the SAM site. That includes every single non-stealthy weapon the US has that can be launched at a SAM site before the launch vehicle itself is shot down. The F-22 is an integral part of the forces required to even begin an air war against any nation with a reasonably modern air defense system. The ability to press inside the outer edges of the air defense zones and carry out air dominance missions is critical. The B-2 and F-117 need fighter support in that environment and the F-15's and F-16 would get shot down before they got anywhere close to attacking the defending fighters or SAM sites.
The new SAM sites eat cruise missiles for lunch too, and even older technology integrated air defense systems are becoming more and more difficult to overwhelm, spoof, jam, etc. The F-22 is again critical in this arena.
Even so, JSF is also required because since the F-22 is so expensive, we'll only have a few and will need to send in cheaper aircraft to carry out missions after the stealth planes have opened up holes in the IADS. Right now, those planes in the USAF are the F-15 and F-16 (and A-10), but once again the SAM threat is big enough to make this quite risky. JSF will provide a platform similiar to the F-16 but stealthy enough to operate closer to the SAM threats while carrying out a wide variety of missions.
The USAF doesn't need this capability tomorrow or next week, it needs it today. China is toying around with the newest Russian SAM systems and Russia is marketing them to a great number of smaller countries as well. They don't take too long to ship and set up either, so we could face a current-generation threat in any country we may possibly be in conflict with.
A last example of where we need the F-22 is in national defense. The F-22 can loiter and get to a given area faster than our current fighters. When there may only be a few minutes to get to an attacking force, whether it's fighters, bombers, cruise missiles, or a terrorist in an airliner, speed matters. The F-22 is very fast.
The USAF is behind, period. Only the integration of our entire force structure and the sheer size of our military is keeping us effective, but an opponent with current-generation defenses could make it much much more difficult.
