You can control the color of the land, and the height (and color) of the bars separately with a block map, but I don't think that's possible with a prism map (in a prism map, the height & color of the land would both be tied to 1 variable, I believe).
: I had cross-posted this to SAS-L and Joe Matise and Nat Wooding got me sufficiently close to what I am trying to do. It doesn't meet my specs 100%, but definitely comes close enough for my current need.
To keep the height standard across graphs I created a dummy fips code and assigned the maximum value to it.
I set the colors with pattern statements and then used area=state to assign the patterns.
Finally, I included a relzero option to have states with no data show zero frequencies.
data usmap; set maps.us end=eof; output; if eof then do; state=99; statecode="un"; segment=1; x=.0950000000; y=.1600000000; output; segment=2; x=.0949999999; y=.1599999999; output; end; run;