The radials were inferior and did not have similar power. That is why all Allied main fighters and bombers were equipped with water or oil cooled in line or V configuration engines that could out perform any radial that by then belonged to the early era of flying. If radials had been so good, and able to be developed further, then they would have been.
Look at American stuff again. Radials are
everywhere. They were still fitted in high performance fighters into the fifties; look up Grumman's Corsair, which makes a Spitfire look slow, expensive, hard to fly and unreliable.
Even the workhorse P&W 1830(DC3 engine and bomber, so it's like a truck motor compared to a racecar) makes 1200hp when supercharged. A radial engined DC3 is still the most cost effective way of moving 3 tons of stuff of short grass strips.