Can it be that you’re confusing accent and pronunciation, Hal? Whenever somebody speaks a foreign language they have an accent no matter how hard they try to pronounce the words correctly. So there was no chance for Kennedy to get his „accent“ right. Even if he’d pronounced all the words perfectly, he’d still have had a foreign accent as anybody else would have. It’s an uphill battle to get rid of an accent. Only few people manage to. It’s easier to get rid of a bad pronunciation but that, too, requires practice. As far as I know, Kennedy hadn’t learned German which means that he was probably confronted with the language for the first time. It may have been easier for learners of German who have had some training to say that sentence but not for him. That’s why I think he did a fairly good job given the circumstances. Just saying...
Maybe his Harvard accent prevented him from providing the proper accent to the phrase. I myself could have delivered it better...I KNOW I could! I've always been good at mimicking the speech of others, to a degree. It's a gift! Harry