You need to buy the ANSI OS1 and OS2 standards. You can get them here
The 18 cubic inch nonmetallic box Jeff mentioned is probably typical of what is used in most new construction for a single switch or receptacle. A 14 cubic inch nometallic old work box is probably most common for upgrades. The main difference between the two is the internal height is less in the old work box. Although these two are probably the most common, they are a lot of other variations. Some boxes intended for tight spaces have a depth of only 1". You may want to take a look at more manufacturers' catalogs to get an idea of the variations. Some of the major brands are Carlon (non-metallic) and Raco (metallic), and Red Dot for exterior boxes.
Pay close attention to the horizontal spacing between mounting holes for gang boxes (2 or more switches). It is less than the width of a single switch box. IOW if you make the width of your devices the same as the width of a single switch box, they may not fit in gang boxes.
The actual use of the boxes is governed by the local electrical code. The code varies from state to state, and sometimes within states. But it is almost always based on some version of NFPA 70, the National Electrical Code (NEC). The number of current carrying wires coming into the box will affect the minimum size permitted. You can get a copy of the current version of the NEC from the NFPA
You may want to look at the dimensions of competing products for the US market as well.
Are you familiar with the other aspects of producing a product for the US market, including certification by a NRTL like UL or ETL?