Edition: U.S. / Global   By ROY BLOUNT Jr.; Roy Blount Jr.'s
most recent book is ''Now, Where Were We?'' His first novel,
''First Hubby,'' will be published in June. Published: February
11, 1990   By Richard Condon.  300 pp. New York: Simon &
Schuster. $19.95.  The imminent legacy of Reaganism: an America
governed so effectively by fat cats and imagemongers that the
Constitution is abandoned, the District of Columbia is
obliterated by a private-sector nuclear device, royalty is
instituted and the figurehead chief of state is Caesare (Chay)
Appleton, a Reaganesque and Ollie Northern hero of the
Nicaraguan Conflict, whose trademark is a homburg hat worn -
even into battle - sideways.  Richard Condon has a new novel,
''Emperor of America.'' Its premise is the above, all of which I
buy, except for the hat.  In my view, a popularly tenable vision
of national Republicanism as both ludicrous and menacing is at
least 10 years overdue. And who better to provide such a vision
than Mr. Condon, whose witty and highly rea