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As I said "I am considering ISKCON only for example." ISKCON isnt really mainstream Hinduism. ISKCON is more of a re-packaging of Hinduism for the western world and was founded by a person called Sri Prabhupada in the US in the 70's. It quickly turned into a fad in the 70's and thats how it gained instant popularity (it wasn't always about understanding or acceptance of Hinduism but for many it was more of a fashion trend).
Just like Rajaneesh's "Osho", ISKCON came to India from the US not the other way round. And except for its association with Hinduism it has little to do with India. I was considering the case of ISKCON because outside of India its among the only few most visible Hindu organizations.

Thanks for the background on ISKCON.

What are the major "really Hindu" missionary organizations, then?