The NSA does not require permission from Congress, the White House or anyone else to retailiate. More often than not, these threats are responded to in kind.
https://www.washingtonpost.com/world/national-security/us-cy...
https://news.ycombinator.com/item?id=22291621
The US is still the only Tier 0 cyber power. Its capabilities in this area are unmatched.