Huh ?
All those figures tell you is that only 12.4% of Muslims in the US are Arab. It says nothing about what percentage of Arabs in the US are Muslim. 100% of the Arabs could be Muslim according to these statistics,and they could still only make up 12% of all Muslims.
OK here you go:
63% of Arabs in the United States are Christians, according to an article at Opinion Journal (WSJ)
http://www.opinionjournal.com/taste/?id=110008591&mod=RSS_Opinion_Journal&ojrss=frontpage