If we stop, how do we make everyone else stop? We can't. So we're not living in a world without spying, we're just living a world where we're at competitive disadvantage to other entities spying on us.
Yet, somehow, dozens of governments that do not spy, because they do not have either the resources to do an effective job of it, or they do not have a mandate to do it, manage to continue to operate. The economies they govern continue to operate. Some of them very prosperously.
Spying by the US government could be cut back VERY sharply and do the US no harm, especially against those governments that are both friendly and that cannot support an effective spying mechanism against the US.
There is a ton of Hobbesian bullshit floating around here. We'd be cheating on all our treaties, too, just because some countries do that, if this whole "state of nature" bullshit actually applied.
Which countries are these? As far as I can tell, every country in the UN has an intelligence agency. Which would mean they spy on somebody, and "effectiveness" seems like a bit of a weasel-y standard.
I expect the signals intelligence effort to be proportionate and be similarly militarily relevant.
Let's say you have a sack of potatoes for that IE 'sploit. Now you have to target it, plant it, exfiltrate data, analyze the data, and provide a context for it among other data gathered, store the data and the analysis, etc.
Compare this to Latvia spending a serious fraction of the military budget keeping, maybe, a couple obsolete, militarily irrelevant, and expensive to maintain Russian helicopters flying. There is a level below which simply saying that you have an air force, or signals intelligence, amounts to nothing of any significance.
Many many nations are in that condition, or are able to do no more than haphazardly tap their own switches and harass some dissidents.
The scale at which the NSA operates is commensurate to that of a navy with a dozen carrier battle groups. Even China cannot put an air wing on one antique (ok, "vintage") carrier. Nobody on the whole planet operates the way the NSA does. The people of the US have vast scope to change that before it even comes close to affecting a balance of effectiveness versus actual adversaries, never mind being in all our supposed freinds' pants.
By diverting the resources currently used for hacking towards securing. Instead of spending billions in discovering (or injecting) vulnerabilities, why not spend money in fixing and securing infrastructure for all?
* Make an open-source scanner that reports (to the user) vulnerabilities in user's hardware / software.
* Spread awareness about security to the general public. This includes making them aware of the above two, as well as low-hanging fruits such as "stronger passwords", "don't reuse passwords", etc.
* Have regulatory bodies that shame / ban manufacturers that don't publish security updates. I am not a fan of regulation, but this is much more appropriate regulation than banning manufacturers for designing round-corners around screens.
* Create an agency where white-hat hackers can independently submit their findings and sponsor their work.
These are just the top off my head; would love if someone criticizes them.
* Even private vulnerability research venues don't reliably publish to the public. When vendors pay bounties, they often keep the vulnerabilities quiet.
* NSA already does security awareness. For instance, they publish a highly-regarded series of documents on secure standard configurations for Unix and Windows systems.
* NSA can't regulate industry; they have no such authority.
* You're really comfortable with the idea of NSA outbidding private venues for vulnerabilities? (Note that the USG already does sponsor "white hat hackers" through the DARPA grant system).