Jim D.and Armen,
The meaning of the "God shed his grace ..." line is clarified by the context of the whole line. If it were past tense, it would be "God shed his grace on thee and crowned thy good ... ." As the full line is written, it is obviously a plea to God, i.e., with an understood "May," as though the author is saying, "America, America, [may] God shed His grace on thee and crown thy good with brotherhood... ."
As much as I adore Ray Charles's version, from a musical and emotional standpoint, he does obscurethe meaning of that line when he says, "and won't you crown thy good with brotherhood ... "

BTW, I think the second verse--especially the last two lines--is one of the best parts of the song. It is this aspect of humility that makes it a fitting national anthem--not the kind of chauvinism that is reflected in so many "patriotic" songs.