As flawed as the US economy is, at least there is still something resembling a market price for basics like a loaf of bread. Yes, you can claim that the USSR wasn't the socialist ideal, however moving further from that claimed ideal results in a more productive economy. To the extent that the west is increasingly centrally planned, it has become relatively less productive.
Things aren't binary though. No one is saying the US isn't "real capitalism", they are just specifying what type of capitalism it is. But that's a very different than saying there's no true Scotsman. There's a reason one is a fallacy and the other isn't.