Over simplification from you, again. MacArthur wanted to lay down a string of A-bombs along the Yalu to block Chinese intervention. And we were already engaging Chinese flagged Migs piloted by Russians.
MacArthur had already turned down Air Force proposals to fire bomb North Korean cities,[32] and suggested that atomic bombs could be used to isolate North Korea by taking out bridges and tunnels. The Army staff considered this impractical.[30][33] On 28 July, the Joint Chiefs decided to send ten nuclear-capable B-29 bombers of the 9th Bombardment Wing to Guam as a deterrent to Chinese action against Taiwan.