They were grotesquely outnumbered by a determined foe and the sneaky landings bypassed the most concentrated areas of the German defense.
You are missing some critical information that has led you to an incorrect conclusion. Allow me to explain it to you.
As for the US army, it was well trained, but not as thoroughly as that of Germany. I cannot speak of the Russians because I know little of how well they were trained, but I do not think all that well, as so many were quickly pressed into service, from what I have learned. There were several reasons for Germany’s demise, most of which had little if anything to do with the quality of the training that soldiers on either side received:
The German army’s doctrine for war was badly flawed. They armed the bulk of their army with bolt action rifles (no match for the majority of their enemies who used semi or fully auto weapons) and supported them with MG fire from the rear and advancing mechanized units. While this works fine for blitzkreig, especially in open areas, it sucks when fighting an enemy army which is better armed in slower moving combat. Remember also, that very few German soldiers had MP40’s. They were mostly in the hands of officers and squad leaders, while the advancing Americans and Russians used Sphagins, Thompsons, M1 Garands, M1 Carbines, etc. A bolt action rifle is not a match at less than 300 yards for an M1 Garand, and it’s a suicide weapon against an M1 Carbine at under 200 yards, all other things being the same, that is. Once the Germans were no longer the aggressor for the most part, thier capabilities suffered. When it came to foot soldier combat, the Germans were outgunned.
Also, American and British bombing of German manufacturing and transportation facilities crippled Germany badly. Not long after they built it, it got blown up. It is impossible to conduct a war with continuously destoyed factories against the most industrialized nation in the world (US) and the immense human resources of the Soviet Union.
Furthermore, partly because of the superior manufacturing capability of the US, and because of the superior tank warfare tactics of the British as seen in N. Africa, the Germans were outperformed in mechanized warfare with the exception of their use of blitzkreig early in the war. The Battle of Britain cost Germany badly, where the RAF kicked the crap out of the Luftwaffe despite the terrible disadvantages of failing airplane parts and being bombed by Germany. Over mainland Europe, the US air power shamed Germany’s already deminished Luftwaffe (thank you Britain).
Add to this the fatal mistake of declaring war on the Soviet Union and bogging themselves down in a churning, agonizing front on the east when they were no longer able to properly supply their forces thanks to US and British bombing, and you can see that Germany was not defeated because the Allied troops were better trained. It was for many reasons, having little to do with training.