> It is "a guess" at best, and that guess won't be correct most of the time, unless you know the word already. And when you don't, you'll be dealing with all kinds of Cansas/Arcansas and although/drought/through/bought/cough/enough most of the time.
"Most of the time" is an exaggeration. English is (sadly) less strictly phonetic than many other languages, but still highly phonetic. Nearly every word in your own comment can be pronounced phonetically.