Japan, for example. The Scandinavian nations provide further instances. Type one nations seem, on the evidence, to be the easiest to keep in a state of harmony, though harmony does not follow automatically from type one status Japan has had a very violent history. The usual objection made against type ones is that they are dull, missing the fizz and excitement of diversity . A monoracial, multicultural society.
Obvious cases are Lebanon and the old Yugoslavia.
The people of Lebanon are almost all Arabs, but have numerous deep cultural divisions most notable, those between Christians, Muslim natives, and Palestinian-Arab refugees. Nigeria, with its Christian south and Muslim north, also fits here, I believe. A multiracial, monocultural society. The U.S.A. is the outstanding example, with some qualifications noted below. Other nations founded by Anglo-Saxons the U.K., Australia, New Zealand are more or less type threes, with pockets of exception like Northern Ireland.