What does the entry called "Designated countries for regional patents" mean (in Google Patents)?
Can you make your U.S. patent international by simply designating some other countries in your filing?
Designated countries only applies to PCT applications, not to US applications.
Designated countries are those states in which a PCT application may subsequently enter national or regional phase. That is, if a state is not designated, no national or regional phase entry application can be filed later from that PCT application.
There are four regional patent offices which may be designated: ARIPO (roughly covering English-speaking Africa), EAPO (roughly covering Central Asian countries), EP (roughly covering Europe), and OAPI (roughly covering French-speaking Africa).
Before 2004, it was necessary to select which states you wanted to designate. However, since 2004 all PCT contracting states and regional offices are automatically designated in the request.
Designating a state does not mean you have an application in that state. It simply means you have the option of subsequently filing a national or regional phase application.