There's a lot of cons to multicultural countries.
Look at Japan, it's primarily homogenous and they have one of the lowest crime rates in the world.
Then you look at Paris, The US, and other multicultural countries and they have extremely high crime rates.
A lot of Africa's problems right now are because Europeans put together different African ethnicity into one country even if they didn't like each other.
Homogenous countries with one culture are usually better.