Is NSA spying really about blackmail?

If the NSA is spying on foreign leaders so widely and thoroughly, actually recording the conversations, not just the numbers being called, and submitting the recordings to keyword searches, isn’t it likely doing the same thing to leaders in the US? And if it is possible to imagine that the NSA is enabling the blackmailing of foreign leaders, isn’t it equally possible that the same thing is going on domestically?
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