The RSS is a fascist paramilitary founded in India in 1925 with the goal of establishing a Hindu nation. Its members are uniformed and armed. It has approximately six million members.
It has produced many subsidiary organizations which work to infiltrate society at every level: religion, politics, courts, police, universities, and so on. The RSS and its subsidiaries are collectively known as the Sangh Parivar, meaning “Family of Organizations.”
The RSS’s  organizational founders interacted with European fascism, even traveling to Fascist Italy to meet Benito Mussolini. Praising his institutions, they declared that the RSS was of a similar type. At the outset of World War II, they praised Nazi racial policies as a “good lesson” to “learn and profit” from. They named non-Hindus in India, particularly Christians and Muslims, as “foreign races” and “internal threats” who should be stripped of citizenship rights and even eradicated. This supremacist ideology is called Hindutva and was coined by Damodar Savarkar
Since its earliest days, the RSS has repeatedly provoked anti-Muslim and anti-Christian violence throughout India. Its followers are implicated in terrorist bombings, assassinations, and multiple outright pogroms which have left, at minimum, tens of thousands dead. This includes the anti-Muslim pogrom in Gujarat in 2002 when now Prime Minister Narenda Modi was the Chief Minister of the state. Women are targeted for mass rapes before being butchered in these pogroms. 
Modi himself is a lifelong RSS member as have been, at times, up to 75 percent of the ministers in his cabinet.
Major RSS subsidiaries included the Vishwa Hindu Parishad (VHP, a religious wing) and the Bharatiya Janata Party (BJP, a political wing). The BJP, in power with Modi as the head of state, closely coordinates its political agenda with the goals of the RSS. It has altered educational policy, crafted legislation criminalizing religious freedom, targeted dissidents, and generally stripped away fundamental civil and human rights.
The BJP has an international wing called the Overseas Friends of the BJP. The RSS has an international wing called the Hindu Swayamsevak Sangh (HSS). The VHP has international wings generally named after the country in which they operate such as VHP A or World Hindu Congress -A.
All three of these major Sangh Parivar organizations operate extensively within the United States. Executives in the BJP, RSS, and VHP regularly travel to the US to both speak at major events hosted by their American counterparts as well as tour American Sangh Parivar organizations. American Sangh Parivar groups, which work closely with their Indian counterparts, are deeply involved in attempting to influence US foreign policy towards India, elect associates to political office, and even change educational curriculum.
The goal of the Sangh Parivar in India is to infiltrate and control society and their presence in America raises similar concerns.
They also have advocacy organizations such as Hindu American Foundation which defend them in media and political arenas 
The Overseas Friends of BJP has recently registered itself as a foreign agent in the US to legalize its attempts to influence US policies 
They have 2 members already in the House of Representatives – one from Hawaii and the second from the Chicago area who attend HSS sponsored events and are heavily funded by the Hindutva network in the US
CIA calls VHP and Bajrang Dal as religious militants and RSS as a nationalist organization 
Hindutva infiltration is very heavy in the educated upper caste Hindus in India. Tens of thousand of RSS sympathizers come to the US every year on student and H1b visas. 
Moderate Hindus have started to organize themselves to resist Hindutva supremacist infiltration in and take over of Hindu temples and professional associations of Undian Americans such as physicians, engineers, etc.As the Security agencies are not monitoring Hindutva groups as much as they should and because of their extensive infiltration in the US, Hindutva RSS is now the main foreign religious extremist threat in the US