See answer below

a. the future/ the future of the American Republics/ American Republics/ serious danger
b. the phase/ the first phase/ the first phase of the invasion/ the landing/ the landing of the regular troops/ regular troops
c.national policy/ our national policy/ our national policy in foreign affairs/ foreign affairs/ a respect/ a decent respect/ a decent respect for all nations/ all nations/ for all nations/ for all nations, large and small

See sample answer below.

“That is no vision of a distant millennium.”
Head noun: vision
Modifiers: no, of a distant millennium
Head noun: millennium
Modifiers: a, distant