I have never noticed any distinct difference in the length of the first vowel in “ladder” vs “latter”. In most American dialects, the two words are indistinguishable in casual conversation except by context.
Powers &8^]
Both /t/ and /d/ get reduced to [ɾ] between vowels. As [ɾ] is voiced, I don’t see why the vowel would be longer based on the original phoneme.
As I said, I definitely do not distinguish in any situation, and have never percieved anyone doing so. Latter/ladder and writer/rider are perfect homophones to me.
One does not “correct,” Cecil.
If one reads what appears to be an error from Cecil, one must ponder what lesson The Perfect Master wishes to teach by an inclusion of what might be, from someone else, an error.
My W is aspirated. Doesn’t everybody do that? 
If I speak the words to a mirror, I’m whistling the W.
I remember waaaaaay back in the sixties, when The Beatles were first exploding in America, that there was a brief “scandal” over whether they were either secretly Americans after all, or were purposely singing like Americans as a sort of manipulative trick. Having grown up for several formative years in England, and spent a great deal of time with British entertainments, I thought the complaints were obvious nonsense, because I could clearly hear British accents as they sang. Even in their first hit here, I Want To Hold Your Hand, the word “Your” was very clearly pronounced with the soft British R, and not with the hard American-style R.
While I also know that SOME producers encourage their performers to do various things to ingratiate themselves for the sake of foreign sales, it’s usually not nearly as pervasive as to consist of straight up imitations.
Someone above mentioned that the singing process itself, alters pronunciations as a sort of side affect, and requires careful listening if you want to tell the difference between someone altering their home accent, and someone who is actually singing IN their home accent.
There is no such thing as a single American accent, any more than there is a single British one, just a collection of various fluctuating elements that people associate with Americans in a general way.
And by the way, it isn’t just singing that triggers many people to pronounce things differently. Many people show big shifts when they are talking on the phone, or speaking into a microphone, or just shouting. The more slowly someone speaks, and the more calmly, the more likely they are to say “little,” rather than “liddl” for example.