Should they be more open, though?
They have a nice society going on, their way of life, customs and traditions, they want to keep having them. Would an influx of immigrants help?
It's not like every place is like the US (a vast country with room to spare, composed by tons of different ethnicities, living on the land of the previous inhabitants, and with a powerful enough economy to assimilate a lot of immigrants). Not to mention: the US immigrants came to the place in ages of SLOW transportation and over a period of 400 years (with some ramping up in the 20th century). Nowadays, especially in Europe, immigration ramps up in a couple of decades or less. And, given the huge numbers, they don't even need to be assimilated that much -- if you can work in a place with millions of fellow X-speaking immigrants, and easy access to websites, tv etc in your language, why bother to learn english or change your habits at all?
Consider a thought experiment: would the US be OK with an influx of 100, 200 or 300 million immigrants from islamic countries? Not terrorists, mind you. Just normal folks, that, nonetheless, would soon wish their practices and mindset be respected and reflected in laws (and, since they would be able to vote, it would be): from the right to beat their wives or persecute gays, to refusing education to their daughters? And even darker stuff like "honour killings" that would be sure to want to bring to their new country?
Now, 30% is a lot to be realistic. But if immigration was "open to all", it wouldn't be that far off. Especially since, in the US, almost 100% are immigrants anyway (just over the course of centuries, not over the course of a decade or so). There are places in Europe where the immigrant population rose to 10% or 20% in a course of a couple decades.