One word: jurisdiction. The GU might read my emails, but they don't have the authority to execute 4am raids on my property and kill me with impunity in the name

One word: jurisdiction. The GU might read my emails, but they don't have the authority to execute 4am raids on my property and kill me with impunity in the name of "officer safety" as an eventual consequence of something XKeyScore flagged. At the end of the day, the people who have the guns and the authority to use them against you take a more prominent place in one's threat model than a foreign entity with no jurisdiction.