couple of things, what does it smell like? and how long was it in the fermenter? US-05 is a very good strong yeast and should not leave an acid or acrid taste or smell. cascade can be a little fruity both on the nose and palate but the combination of yeast and hops is a match made in heaven. What was the kit? If it was cascade I would say that you have gotten a dud and will soon understand why I no longer brew kit beers aside from the odd coopers. If you are fairly new to brewing I recommend that you get a packet of yeast some malt and a sterile container and ferment the yeast taking particular note of how the fermenting wort smells and recognising it for future referrence. beer should smell like beer, malty, breadlike and not have any acrid, plasticy, sour smell. If possible do it in a glass demijohn so that you can see how the brew starts off, after a couple of days looks turgid, then after about 5 days starts to clear. Depending on temperatures yeast used etc. I would not recommend leaving if in the barrel for more than 10 days (unless it is a lager and it is fermenting at very low temperatures.) Definetly no more than ten days for an ale using us 05. all the best Trav