No the greatest threat to the American people isn't external. The greatest threat is internal and the massive economic divide orchestrated by the elite super rich over the 99% who continue to lose under a capitalist economic system that subjugates them.
The pittance the elites provide to the middle class has kept them in league with the elites essentially making the middle class unwitting accomplices, complicit enablers to the elites designs and keeping them at bay.
However the elites may have overstepped their malicious ways. The middle class is shrinking in America because of the elites overzealous de-industrialization, outsourcing of jobs to 3rd world countries forcing more of the former middle class into joblessness, home foreclosure and financial indebtedness.
The elites in America got richer in the process and everyone else got poorer.
If the people left and right were to set aside their differences, stopped the unnecessary antagonism toward one another denouncing minorities, blacks, browns, immigrants recognizing it's the old divide and conquer strategy devised long ago by elites to keep all those "others" fighting against one another, then a necessary class war could ensue bringing to an end the elites stranglehold on power. A class war by the majority aimed directly against this elite minority could change the existing corrupt system into a more fair egalitarian system representative of the majority.
As to the Stockwell quote above on the "establishment" I'd add elites who are one and the same.