Melchior

On a quality of design or manufacture the Garand and K98 were pretty much equal indeed. Maybe extra points for Mauser being able to produce the K98 in both number and quality. The M1 Garand almost certainly was a better weapon than the K98 in a tactical sense though. Especially when one realizes quantity of firepower has often done more to secure victory than pin point marksmanship. The reality was most guys during the war couldn't hit a man sized target beyond 200m and within that it would often take some 30-40 rounds to still do that. The British liked to joke in the 18th Century it took a man's own weight in musket balls fired to actually kill him. Most bolt action rifles were gratuitously effective to ranges out over a kilometer and even the Garand was effective to 600-700 meters. Even a trained marksman has difficulty hitting targets at those ranges. With this in mind, it's really not surprising that the US Army would equip their soldiers with a weapon that gave them the equivalent fire output of 3 bolt action rifles but in one weapon. They weren't the only ones to notice this either, as the Germans and Russians also pushed hard to widely employ semi automatic or automatic rifles for their forces.

The problem was no one was about to tell the pilots of their Air Force they weren't really accomplishing as much as they thought. Every side during the was notorious for inflating kill counts due to the difficulty of verification and for plain ol' propaganda. The R&D divisions of every side almost certainly knew what was going on, but they weren't about to march to the nearest airbase and say "Yeah remove a couple of those kill tallys from your fuselage." In terms of cost efficiency i'd honestly every Tank Destroyer the Wehrmacht ever fielded except for pointless ones like the Jagdpanzer IV pretty much got them the bang for buck they needed more of. The StuG III and Hetzer deserve special recognition paticularly for allowing the Germans to effectively extend the lifespan of the very outdated Mk. III and 38(t) chassis.

The Allies had pretty much done all that for you. The Western Allies actually had a lot of trouble keeping the logistics train moving fast because of all the bridges and rail yards the 8th Air Force had destroyed. As it was they couldn't capture an intact deep water port until Le Havre and even then their were no rail roads in good condition to keep a long line of constant supplies going. This resulted in things like the Red Ball Express which had mixed results at best and at worst wasted more fuel and supply than it delivered. The Allies were never really stretched for resources though, they were just kind of sad they couldn't catch retreating German units fast enough. Bear in mind that every time the Wehrmacht had tried to perform a gradual withdrawal the Russians always attacked with full force and it would then turn into a mass rout. The Soviets were obsessed with finding weak points in the German line and giving up sections of ground was often an obvious sign of a weakness. This was a major reason Hitler wasn't willing to let the 6th Army just up and withdraw from Stalingrad. Holding the Balkans arguably allowed guys like Kesselring to hold out in Italy for as long as they did. Very, very successful delaying actions if ultimately fruitless. Nobody in Germany was going to make peace as long as their were still 3.3 million soldiers ready to fight the Russians. Hitler dead is not going to be enough to satisfy the Allies either. They said they wanted the complete and total capitulation of Germany and nothing short of that was ever going to be acceptable. I don't buy the idea that the Allies would have changed their minds with mounting casualties. The Battle of the Bulge was an attempt to exploit that myth and not only did it fail to find such weakness, the Americans were actually happy to see the German Army expose itself in such a bold faced offensive. They considered it an opportunity! True enough. Though it's not like holding the beaches was ever a realistic option either.

TBH the differences between German and American units by 1944 could probably be considered academic. Both Armies had a fond appreciation of the importance of good NCOs, flexible leadership, and arming as many men in the squad with as many rapid fire weapons as possible. In short it basically should be a coin toss barring other factors. We're looking at two well trained, well equipped, modern Western Armies. Ze Germans weren't magic super soldiers and the Americans weren't scrappy underdogs.

Bear in mind Japanese tactics were based on operations planned against the Chinese, who were even farther behind the Japanese on a tactical level. The Japanese knew they were behind the West in equipment, but they had hoped to make up for it by using the Navy to secure distant regions of the Pacific, and then fortifying the hell out of those positions so they could somewhat mitigate the tech and manpower disparities. Guadalcanal was an ill thought out offensive campaign with an even more ill thought exit plan. Up until that time though a combination of surprise and luck in previous ops had led the Japanese Army into believing it wasn't as far behind as it thought, and that sheer mass of force and the magic spirits of uber samurai or something would lead them to victory.