Why Germany may not have unrestricted immigration...
There is a major difference between the USA and Germany in respect to immigration. The United States of America are a country built upon the principles of liberty, individualism and self-caring. This is totally opposite to contemporary Germany ideologic stand.
The United States of America can easily open their borders and should so, because everyone entering the country is on his own and everything he does is in his responisbility. This is not the case in modern social-democratic Germany.
You think this is not true? Well, simple example, immigration. Our parties are arguing about a law to open Germany's immigration principles at the moment and they do it in the interest of all Germans! In Germany, immigrants are not responsible for their own life, instead they are nurtured by the state from the beginning. When you become a German, you have a "right" on social insurances and welfare, which is exactly the reason, why I am opposed to unrestricted immigration. Those people get tax-payer-money without having done anything. They are fed by the state, thus they are parasites in the first month. I am not against immigration, but I am against unequal immigration in this circumstances.
They don't contribute to their own life, but live on welfare and thereby ruin the few we have left of our social welfare system.
So, there are two possible solutions, either abolish social welfare (which I'd recommend) or put a stop to immigration (latter would be a disgrace and slap in the face of individualism). But there is no way, both will work in the long run.
P.S.: I am not a racist, although some might interpret it that way. And I don't say that immigrants are generally lazy welfare-parasites, it just happenes that with the "self-interested" immigrants, there come the parasites...