You mean during Desert Storm? Stealth was very new (I think the F117 had been used in Panama for the first time though). 8 years later the Serbs were able to track and shoot down an F117. The Russians and Chinese and probably every other defence company aren't sitting still.

Afghanistan had no serious air defence network anyway. The Iraqi air defence network was heavily outdated and under sanctions for over 10 years in 2003. The Libyan air defences hadn't been updated since the 80s when the US managed to bomb Libya with the loss of one aircraft.

The Israelis managed time and time again to overcome the Syrian air defence network. Which is, although not build to its full capacity due to Russia holding back the S300 and now heavily impacted by the civil war, more modern and better designed than anything the US encountered in her recent conflicts. And the Israelis have no stealth aircraft and used their F-15.