It has always only ever taken some honest concerted thought to realize - at any time - all cultures are not equal, and any very large cultural invasion is no different than any other - disruptive and possibly suicidal where it happens.
U.S. intelligence should take the task of researching and identifying all the direct, indirect and supportive players, across the globe, who have advocated, approved, supported or promoted international mass migration.
Meanwhile:
Cuba, China, Madagascar, Vietnam, and Indonesia, often having less than 1% of their population comprised of immigrants. These nations, along with India, Bangladesh, and Pakistan, maintain very low immigrant inflows due to restrictive policies, economic factors, or low, negative net migration.
Of course, no one in their right mind would immigrate to Cuber.