What did the author mean when he said "the cause of america" is "the cause of all mankind

When the author said "the cause of America" is "the cause of all mankind, he is refereeing o the worldwide plight of people under oppressive government and all of those individuals are struggling against them, the struggle for the cause of America is a symbolic statement for the struggle for the cause of humanity worldwide wherever the same kind of circumstances are found. 

glamis thou art, and cawdor; and shalt be what thou art promis'd; yet do i fear thy nature; it is too full o' the milk of human kindness to catch the nearest way: thou wouldst be great; art not without ambition; but without the illness should attend it. what thou wouldst highly, that wouldst thou holily; wouldst not play false, and yet wouldst wrongly win: thou'dst have, great glamis, that which cries, "thus thou must do, if thou have it: and that which rather thou dost fear to do than wishest should be undone." hie thee hither, that i may pour my spirits in thine ear; and chastise with the valor of my tongue all that impedes thee from the golden round, which fate and metaphysical aid doth seem to have thee crown'd withal.  

he lacks ambition.  

he is hesitant.  

he lacks courage.  

he has moral scruples.

we have no idea what story or poem you mean? ?

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