1) Bore sighting --- Practice makes perfect, going to the range and hitting a bucket of golf balls before a round, gives me an edge
2) Sailors who sit on a ship for 6-months are more seaworthy (thus experienced) in many things over a rookie, experience or not. Seasickness, day-to-day drills, & everyday life at sea.
3) Maneuvers by the Captain. Starboard into a headwind, drafting of directional waves, navigation, map checking. The more your sail, the more you know/learn. Thus experience.
Sailors on a ship when it is busy cruising around on patrol, or protecting convoys, or literally anything other than sitting in port, will be doing regular drills and training on the ship. Gunners would practise firing the guns at dummy targets (albeit most likely with blank shells). Navigators spend all day navigating. Engineers spend all day making sure machinery is working right. They don't just sit around until an enemy comes up and attacks them.
Shooting at an undefended town (which is a much larger target than a ship, and doesn't move), probably wouldn't be any better a training exercise than the daily drills. Probably worth the same amount of experience stars as those daily drills are too.
So the Germans get this.
a) German Generals + Technology begin 1939 with Command & Control + 1. Why? Where did they fight? I don't read about Erich von Manstein, Michael Wittmann, Heinz Wilhelm Guderian in a battle.
b) Destroying Poland (who were sleeping farmers) does not count as a battle. Kissing your sister isn't a date. Playing basketball against a midget isn't experience.
c) Defeating France (who revealed later many were pro-Nazi) certainly isn't experience. Mike Tyson fought bums, until Evander Holyfield. Muhammad Ali fought bums, until he got Joe Frazier.
There's more to command and control than just battles. Equipping tanks with radios, ensuring the chain of command is well defined, telephone communications are set up, ensuring all leaders have access to detailed plans, and know what to do when things go pear-shaped. The Germans were excellent at this, the French quite emphatically were not.
The 50,000 German casualties during Fall Weiss would disagree with you about Poland not being a battle. Geography, manpower, better equipment gave the Germans a tremendous advantage over the Poles, but the Poles definitely weren't a walkover. They fought hard.
And France counts as experience if literally anything does. In 1938 France was considered to have the finest army in the world, and on paper there is very good reason to agree with that. They had four million men (most of whom were just as determined to keep the Germans out as their fathers had been in 1914), as many tanks as the Germans had if not more (and far stronger, though not necessarily better, ones at that), and when the Low Countries and BEF are included, a comparable fighter strength to the Luftwaffe. They were defeated because the German generals handled the battle far better than the French generals, not because France was a pushover.
The Americans are disrespected.
--Patton had the "Wow" factor, the real leadership, the 3rd Army was a machine
--Japs had all kind of "experience" trashing 3rd world countries, and military victories leading upto Midway. What happened? American brains.
--American Pilots were & are more brave than anyone on the planet. We fight for a better cause.
--Japs got stuck on their strategy of perimeter defenses, the Yanks only fell for that once.
--Americans had better riflemen than both Gerry & Japs. Per captia, back then, and now, we got lots of Deerhunters who are naturals.
--German leaders could not wrap their brains around "intangibles". There's more to winning than counting tanks, flanks, & munitions. There's intangibles. Bring your winter coats, morale, hope, cause.
You can have all the experience & practice you want, but if you stink, you stink.
The Americans were hardly supermen either. They had their fair share of screw ups, the difference is that they had five times the industrial power of Germany and fifteen times that of Japan, so any mistake they made would affect them less severely in the future. Also, they could afford to give their troops more training than the Axis or the Soviets, because their country wasn't being bombed day and night. More training produces better troops - notice that when the Americans stopped caring so much about training their army, they got whipped in Korea. The exception being the Marines, which kept up their training!
Also I find the part about "Japan trashed 3rd world countries" interesting - in practise doing so would look very similar to your tactic of bombarding an empty town over and over. Yet you then state that the force that did so was stopped cold at Midway. So clearly bombing empty towns isn't really worth the XP that it provides. :)