Ever since the Treaty of Westphalia, the idea of territorial sovereignty has been central to how most of us think about international politics and foreign policy. Although a huge amount of activity occurs across state borders, one of the chief tasks of any government is to defend the nation’s territory and make sure—to the extent it can—that outsiders are not in position to interfere in harmful ways. But for all the effort and expense devoted to keeping harmful influences out, sometimes countries wind up locking and bolting the windows while leaving the front door wide open.
Walt, Stephen. "America Is Wide Open for Foreign Influence." Foreign Policy, April 8, 2019.