What I mean by this is that it seems that there's always an 'enemy' be it the reds, terrorists, japanese spies, etc. Is this a unique quality of the US or something that happens in all countries?
It does seem a depressingly universal phenomenon, part of what moulds our attachment to countries. Compare Britain with the Sots, Spaniards, Irish, French, German, Russians. Or France menaced by the Spanish, Germans, British, Germans again, Russians. Or Germany facing "encirlclement" by some combination of French, British or Russians. And that's without counting lower-grade animosities toward ethnic minorities at home or those who might want to get in, neighboring tribes, colonial subject peoples abroad, or religious or ideological rivals under possible foreign control.
It would be comforting to chalk it down to US exceptionalism. But it's not very exceptional. Europe's past is littered with similar paranoias from the Popish Plot to Soviet special forces agents disguised as women peace activists.
After the end of the Cold War, until 2001, America was without a significant boogeymen. This led people to believe that American-style democracy had essentially won, and that all states would inevitably become capitalist democracies. See Francis Fukuyama, "The End of History."