We have the Charter to rule them all despite disgruntled right wing bigots complaining.
Extremely multicultural nation mostly successful except with our own First Nations.
Over 160 languages spoken in Toronto, light skin is in the minority, the Muslim community here by and large are not in the least troublesome.
Way more headaches with First Nations and alcohol and land rights issues.
Quebec has the biggest issue trying to maintain pure laine ( cultural and language purity ) within an English speaking majority in the country which is officially bi-lingual but resentfully so in some regions.
Multi-culturalism in a national policy and encouraged and supported with funding but NOT importing conflicts and illegal practices like female circumcision is strongly enforced.
For instance Muslims wanted sharia courts because jewish communities had jewish family courts.
The solution....kill the jewish courts. One law to rule them all.

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I don't think the US melting pot has worked at all and the US is now effectively a bi-lingual country with Spanish as a second dominate language nor is there any uniform culture.
Large municipalities are very multi-culture centric with dual street names.
A strong stable ethnic conclave tends to absorb immigrés with the least issue - finding them jobs and getting them settled and on occasion exploiting them which the laws are designed to mute.
We were multicultural from the get go even the First Nations represented a whole lot of languages and cultures and then English and French were welded together with two different fundament types of law ( English Common law in most of Canada and French Contract law in Quebec ).
Then wave after wave of immigrants many of whom settled together.
It generally works here tho can be costly in a place like Toronto due to education issues ( think about 160 languages ).
But fuck it's fun.....all those cool restaurants and parades and cultures - Toronto used to be dull and boring Brit in the 50s - now it rocks as does Vancouver and Montreal and the all have benefitted from the many cultures, the wealth it's produced and stats say the emigrants are far more law abiding in general than the long term residents.
Generally 3rd gen are fully integrated INTO a multicultural society.....not a monoculture. Celebrate diversity.
The key in my view is coherent government support, prevention of exploitation and confidence that one law for all.
Biggest issue for TO is some ingrained bigotry in the cops but then some high profile Human RIghts cases have supported those being profiled. Confidence in treatment under law is critical as is job opportunity.
France has issues as it ghettoizes emigres and unemployment is very high even in 4th generation citizens that are ethnically diverse.
What ever Holland is doing seems not successful being handcuffed by a muslim population only 6% -
We are only 2% nation wide but areas like where I am it's 30% and they've elected a member of parliament so are fully engaged.
We've had a few radicals but not only in that population and far more radicals in First Nations where the reasons to resort to violence are certainly understandable.
I think nations can have a multicultural society if laws are exerted evenly and and an effort is made to provide employment opportunities.
In Canada a person that feels over looked for cultural or ethnic reasons can and do sue under the Charter for discrimination.
Rule of law is key and enforcing it evenly accessible to all.