This topic is old but this is what I found
The USERRA regulations (recently promulgated by the Department of Labor) state: “USERRA applies to foreign employers doing business in the United States. A foreign employer that has a physical location or branch in the United States (including United States territories and possessions) must comply with USERRA for any of its employees in the United States.” 20 C.F.R. 1002.34(b). In a pamphlet entitled Employee Rights When Working for Multinational Employers, the U.S. Equal Employment Opportunity Commission stated: “Employees who work in the U.S. or its territories are protected [by U.S. civil rights laws] whether they work for a U.S. or foreign employer.”
It seems to me that it should apply.