It's too reductive to claim that immigration didn't cause problems, and it's too reductive to claim that immigration is the source of most of the problems.
The cause is a single genetically and socially society allowing mass immigration but not changing society to match the newcomers and/or not selecting newcomers based on culture similarities and/or not bridging the divide.
When you make a mass immigration commitment you need to follow it up with tons of work/money/education/discussion. That's why it fails in Europe but succeeds elsewhere. Then they make it impossible to succeed by limiting discussion and calling it hate speech.
North America has two different approaches. Leave who you are behind and become an American. Keep who you are and become Something/Canadian. Sweden wants it both ways.. leave who you are behind but never become Swedish.