From cpb.gov
Global Entry

Global Entry is a U.S. Customs and Border Protection (CBP) program that allows expedited clearance for pre-approved, low-risk travelers upon arrival in the United States.

NEXUS

The NEXUS program allows pre-screened travelers expedited processing when entering the United States and Canada. Program members use dedicated processing lanes at designated northern border ports of entry, NEXUS kiosks when entering Canada by air and Global Entry kiosks when entering the United States via Canadian Preclearance airports. NEXUS members also receive expedited processing at marine reporting locations.

Does not appear that SXM should be able to process Nexus according to this. Also, it appears if you are Global Entry you are Nexus too as you are already 'pre-screened' as a global entry member.