Will 802.11b/g products purchased in one country work in another?

Maybe. Since most manufacturers don't like making country-specific products, the chipsets used in these products are capable of operating in all 14 channels. However, operating systems and drivers localized for specific countries may lock operation to only the frequencies allowed in that country.

Some products handle this issue by asking the user to specify the country of operation upon first use. In other cases, the user can go into the Advanced properties settings and set the channels used.

See this Wikipedia article for a list of the allowed 802.11b/g channels in major countries / world regions.