The NG B737 cannot fly GPS approaches, RNP/ANP or RNAV yes but not GPS. Some countries allow an LNAV/VNAV overlay approaches but usually only with VOR/LLZ/ADF approaches
Air Canada and Alaskian had GPS CDU units on their Legacy and Classic aircraft and could fly GPS Approaches
You are required to de select the GPS from updating when flying in non WGS84 countries due to map datum errors.
The GPS units fitted to most Glass Boeing B737 are automatic and have no pilot interface, they are unable to show RAIM forecasts as required by an approach cert GPS. Hence the aircraft do ANP/RNP approaches.