Questions arise occasionally on whether a Scout moving to the USA from another country can use the advancements he had earned in that country toward advancement in a BSA Unit.
The answer, which is, "YES HE CAN", can be found in Guide to Advancement (BSA publication #33088).
This policy has recently been revised to make it clear that it applies to advancement by youth in ALL of the BSA's program areas. Although not specifically mentioned, a process similar to that listed for Eagle Scout should probably be used for youth desiring to work toward the Quartermaster Award in a Sea Scout Ship, or toward the Ranger and/or Silver Award in a Venturing Crew.
The following is from the 2013 edition of the book mentioned above:
184.108.40.206 - Youth From Other Countries
Youth from other countries who temporarily reside in the United States, or have moved
here, may register in a BSA unit and participate in advancement. If progress from a foreign Scouting association is to be considered and applied to BSA requirements, then the foreign Scout must meet in person (or over electronic media) with members of the council or district advancement committee, along with at least one adult leader or committee member of the receiving unit. Previous advancement work is reviewed to determine the BSA rank—up to, but not including Eagle Scout rank—the youth is qualified to receive. The candidate must present evidence of membership and advancement from the previous association. Once a rank is determined, it is reported through the BSA’s Internet Advancement or on an advancement report.This procedure applies to all ranks except Eagle Scout, which is not considered equivalent to any other association’s rank. If it can be established that Life rank has been achieved, then the council or district advancement committee can determine which BSA merit badges may be awarded based on previous effort and experiences that meet BSA merit badge requirements as written. This may leave a number of additional badges to earn—required or not—to achieve Eagle. Requirements for active participation, position of responsibility, Scout spirit, the service project, and the unit leader conference must be completed in a BSA unit. This procedure also applies to members of the BSA who, while living abroad, have earned advancement in another Scouting association.