It's not all-or-nothing thinking re: failing to pass the law. A vote count's closeness has very very little to do with how close the outcome actually was. It literally means nothing that the vote count was so close.
I also don't think one case will do it. It'd have to be a trend (people literally snatched up in the night), a policy shift (all copyright abuse starts being enforced because now they have that data), or some kind of tragic action leading to the deaths (yes deaths) of people on US soil.
You may be right. But in my opinion it's not the severity of the action that's brought to light, it's who gets hurt. The elites of the US are usually fine with extraconstitutional shenanigans and human rights violations when they only affect foreigners, or relatively powerless people within the US.
When it affects the domestic balance of power, then you start to see elite consensus building against it, and the wheels of reform start turning. This is how a hotel break-in is more serious than a secret war in Indochina.
It's possible that US elites will perceive surveillance as a threat to themselves. If they don't, you're probably right and then everyone just gets used to it, and any reckoning is kicked down the road for a few more decades.
No one's actually gotten hurt because of the NSA's surveillance, so that's the problem. All of these potential consequences are theoretical. We're trying to string the NSA up on what amounts to pre-crime.
I also don't think one case will do it. It'd have to be a trend (people literally snatched up in the night), a policy shift (all copyright abuse starts being enforced because now they have that data), or some kind of tragic action leading to the deaths (yes deaths) of people on US soil.