How does european style immigration challenge traditional notions of sovereignty and the nation state?

Sovereignty is the power of the state to control the matters of the state internally only and without the interference of external power. Since a lot of people are coming into the countries of Syria, Afghanistan from other countries so these refugees pose a question to the people who have origin from Europe to question whether it poses a threat to the sovereignty of the Europeans and the nation state with their power to control the matters of the state.