Australia of course, it’s a rather odd question.
Australia used to be Anglo-Celtic (very much was prior to WW2) and I know some people like to compare it to Europe saying it has – or had – a “core ethnicity”, but it’s not really comparable at all as a settler society with an utterly marginalized indigenous population, that developed into a very diverse and multicultural place. It is as much an “immigrant nation” as Canada or the US. Such countries are inherently different in their attitude to integration of immigrants than ethno-cultural nation states as the European.
Belgium has always been bi-national and the common tie between them was Catholicism, but it’s still basically an ethno-cultural nation that has received guest workers and refugees post-WW2. As such it’s not really all that different from other European nation states in having significant opposition to immigration. Bruxelles being the EU-capital gives it an international flair, but that hardly changes the fundamentals.
Denmark is at heart an ethnically based nation state that has just taken in some guest workers, refugees and “ in the last 50 years. Large parts of the population isn’t comfortable with the country being an immigrant country at all.
Source: https://www.quora.com/Between-Belgium-Denmark-and-Australia-which-is-the-most-accepting-and-inclusive-of-immigrants