DBA in this question likely stands for Defense Base Act rather than the Davis Bacon Act. The Defense Base Act requires insurance be purchased to guarantee workers' compensation benefits are provided for covered employees working OCONUS locations. The associated clause flows down to all subcontractors so as to cover anyone working under the contract. According to the US Department of Labor (DOL), "all employees engaged in such employment, REGARDLESS OF NATIONALITY, are covered under the Act." (capitalized emphasis added,
Thus it would appear that this act, as interpreted by the DOL, extends to subcontractors, regardless of nationality. If this is a common understanding of the scope of the DBA, one would reasonably expect anyone underwriting DBA insurance would include Non-US subcontracted firms as being within the scope of the insurance coverage since this would be the expectation of the DOL? One would have to contact a DBA insurance underwriter though to be absolutely sure. There would seem to be a number of underwriters for this kind of insurance so contacting more than one might also be an option.
In addition to the usual AAP disclaimer, youshould also consult your legal authorities as well since we don't have the contract/order specifics before us such as order type (T&M, CPFF, etc.) an/or other general/special provisions.