Validity of Volga-Dnepr An-124 Grounding in US
It only makes sense USA enforces the action of Ukraine, if it wishes Ukraine does the same in the future (as noted by @JuanJimenez). Luckily, those countries (states) already agreed to the following terms as part of joining ICAO:

4.2.1 State [Country] of Design
4.2.1.1 The State of Design of an aircraft shall:
a) transmit to every Contracting State which has in accordance with 4.2.3 a) advised the State of Design that it has entered the aircraft on its register, and to any other Contracting State upon request, any generally applicable information which it has found necessary for the continuing airworthiness of the aircraft, including its engines and propellers when applicable, and for the safe operation of the aircraft, (hereinafter called mandatory continuing airworthiness information) and notification of the suspension or revocation of a Type Certificate;
Note 1.— The term &quot;mandatory continuing airworthiness information&quot; is intended to include mandatory requirements for modification, replacement of parts or inspection of aircraft and amendment of operating limitations and procedures. Among such information is that issued by Contracting States in the form of airworthiness directives.
Note 2.— The Continuing Airworthiness of Aircraft in Service (Cir 95) provides the necessary information to assist Contracting States in establishing contact with competent authorities of other Contracting States for the purpose of maintaining continuing airworthiness of aircraft in service.

(Source: Annex 8 to the Chicago Convention; bold emphasis mine.)
That's the legalese for when a country that has designed a plane, finds an issue (e.g., the alleged unauthorized maintenance making those affected not airworthy), shall notify the other contracting states (other ICAO member states).
If any state wishes to ignore that it has been notified that certain planes are not airworthy, will surely have consequences, but this is a better fit for Law.SE.