As we have said in previous reading room articles, a design may be registered for monopoly protection in many countries.
In the UK this is through a system of design registration, but in the US more or less the same goal is achieved by a patent system for designs.
A US design patent may be based on an earlier application in another country.
That is you may file in the UK and on the back of that filing, file later in the US, and claim the date of your UK filing as your filing date in the UK as well.
In order to obtain the benefit of an earlier foreign filing date by claiming priority, the US application must be filed within 6 months of the earliest date on which any foreign application for the same design (even if it was called something else, e.g., Certificate of Registration) was filed.