If after WW1 all of europe shared tech and actually worked together
when do you think these would be made in large numbers
Weapon (OTL equivilent)
Heavy bombers (flying fortress size)
Large Aircraft Carriers (like the USS Midway)
Jet Fighters (hurricans)
Heavy Tanks (Panthers)
Assult Rifles (Stg-44)
Advanced Subs (OTL 1944 ones)
Helicopters (Korean war ones)
Atom bomb (self explanatory, Eintstien has told europe about the Bomb rather than america)
If Japan becomes a major rival, then you could certainly see an impetus for a lot of these (not all). A China-focus from Europe could certainly help here, and if the idea that a pan-Pacific War is coming gains credence, then large aircraft carriers able to operate as mobile airfields, heavy bombers built for range and endurance, advanced submarines for trade interdiction or sneaking up on the battlefleet, and better rifles etc from experience.
Some of these technologies require foundation technology so are hard to do before the 1930s - helicopters were at the point of being viable in Germany by 1939 and if the Allies had not bombed the Focke-Agelis factories would have been much more numerous in use by the Nazis, so you could certainly have much more widespread and advanced helicopters by 1940 or so.
Vickers Heavy Tank shows that the design concept was certainly possible to be pursued - OTL it was abandoned as not having a purpose so continuing this route would need a clearly identified role for it
Best Regards
Grey Wolf