Cascade is a great all purpose hop for American ale styles. It can be pungent at first but it does get better with age. I like using it as a bittering hop. I tend to be patient and am not in a rush to carbonate as soon as the beer hits FG, so I tend to start drinking them after these off flavors have mellowed/dissipated. Please understand, I'm not claiming you did that, I'm just saying you got this flavor early, but it dissipated, which means you may have started drinking this batch before the mellowing took place.
Note that other particulate can drop out over time, too. Yeast bite is a common flavor experienced early in a batch. It has a harshness to it (hence the term "bite"). Also, Dry hopping imparts tannins from the hops, which can add to the perceived bitterness. As the beer ages, these tend to drop out as well.
You can try brewing the same batch again, and split it into 2 kegs. Drink 1 right away, and save the other, to see if you get the same results (early == bitter, late == smooth).