Resp:
Their missions were different; one the aggressor, the other the defender. So it makes sense that tactics could/were quite different. Again, it was important to adjust the tactics (as Gen Doolittle did by directing his fighters to attack aircraft on the enemies' airfields in the ETO) as the war progressed. Also, long range fighters were under threat of attack for a longer periods (ingress and egress, again in the ETO) due to the greater time of flight, and the the fact that their paths took them over the same enemy territory twice. In the beginning, Germany didn't need much air assets to protect Germany. However, it wasn't long before Germany was attacked regularly. In doing so, the Luftwaffe were forced to assign large assets (taking them away from other areas) to its Country's defense; strategic as well as tactical.