There's really no reason to ever buy anything from Johnie Walker. If you want to drink whisky on a budget in the US, don't buy Scotch.

You'll do much better in the US with a Rittenhouse Rye, or Buffalo Trace bourbon. Hell, even a basic Jameson is better than Johnie Walker Black.

The Johnie Walker Green is a respectable whisky, but like so many high-brand respectable whiskies, it can't punch its weight with other things in its price range. (I've never tried the Blue, admittedly.) That's the same issue with e.g. the Jack Daniels range. It's not that it's bad for mixed drinks, but you can get some genuinely good stuff for cheaper -- stuff that'd so good you'll feel bad about pouring it into a cocktail.