CANCELLED PLATE

The year, 1793, in which Blake issued America had been active politically. In France Louis XIV had been guillotined and a reign of terror had ensued. Britain had gone to war with France and for much of the next twenty years would be under threat of invasion by France. Blake had given up the idea of having his pamphlet The French Revolution published by Joseph Johnson. He turned to another means of commenting on revolution through prophecy and pictures in his illuminated book named America.
 
The insecurity he felt about expressing himself regarding the political situation is stated in his notebook where he recorded personal thoughts and ideas which would eventually work their way into his art:

Miscellaneous Prose, Memoranda from the Notebook, (E 694)
     "I say I shant live five years
     And if I live one it will be a
     Wonder    June 1793"

Before he issued the eighteen plates of America in the fall of 1793 he cancelled three plates to eliminate explicit mentions of King George III or other statements or images which may be construed as seditious. It seems that Blake found that he could avoid opening himself to the possibility of censorship by leaving unsaid thoughts that the reader may understand without explicit reference.
 
Blake's methods are explained by David V. Erdman in Visionary Forms Dramatic:
"The action of the poem-picture is larger and more complex than would be indicated by the pictures or the words taken separately, for these point not at each other (as in the usual picture book) but beyond themselves. The artifact only opens the sensory doors to the mental theater.
In other words, the text is not there to help us follow the pictures, nor the pictures to help us visualize the text; both lead us to an imaginative leap in the dark, a leap beyond the dark and the fire - from perception to Intellectual Vision, a last judgment in which fools perish." (Page 92) 

America, Plate b, (E 58)
[Canceled Plates]
"Reveal the dragon thro' the human; coursing swift as fire
To the close hall of counsel, where his Angel form renews.

In a sweet vale shelter'd with cedars, that eternal stretch
Their unmov'd branches, stood the hall; built when the moon forth,
In that dread night when Urizen call'd the stars round his feet; 
Then burst the center from its orb, and found a place beneath;
And Earth conglob'd, in narrow room, roll'd round its sulphur Sun.

To this deep valley situated by the flowing Thames;
Where George the third holds council. & his Lords & Commons meet:
Shut out from mortal sight the Angel came; the vale was dark     
With clouds of smoke from the Atlantic, that in volumes roll'd
Between the mountains, dismal visions mope around the house.

On chairs of iron, canopied with mystic ornaments,
Of life by magic power condens'd; infernal forms art-bound
The council sat; all rose before the aged apparition;            
His snowy beard that streams like lambent flames down his wide breast
Wetting with tears, & his white garments cast a wintry light.

Then as arm'd clouds arise terrific round the northern drum;
The world is silent at the flapping of the folding banners;
So still terrors rent the house: as when the solemn globe        
Launch'd to the unknown shore, while Sotha held the northern helm,
Till to that void it came & fell; so the dark house was rent,
The valley mov'd beneath; its shining pillars split in twain,
And its roofs crack across down falling on th'Angelic seats."

America, Plate 4, (E 53)
"Appear to the Americans upon the cloudy night.

Solemn heave the Atlantic waves between the gloomy nations,
Swelling, belching from its deeps red clouds & raging Fires!
Albion is sick. America faints! enrag'd the Zenith grew.
As human blood shooting its veins all round the orbed heaven     
Red rose the clouds from the Atlantic in vast wheels of blood
And in the red clouds rose a Wonder  o'er the Atlantic sea;
Intense! naked! a Human fire fierce glowing, as the wedge
Of iron heated in the furnace; his terrible limbs were fire
With myriads of cloudy terrors banners dark & towers             
Surrounded; heat but not light went thro' the murky atmosphere

The King of England looking westward trembles at the vision" 

Library of Congress
America
Cancelled Plate b

Wikimedia Commons

America

Copy M, Plate 4