The data is clear. Poland has zero illegal immigrants and zero terrorist attacks. This is opposed to Western European countries like Germany and France which have rising crime rates and Jihadist terror attacks after they opened their borders to so called Muslim migrants.
Interestingly enough there are similar statistics found in other Eastern European nations like Austria, Hungary, and Romania. While the EU has tried to force a general opening of all member state borders to migrants, the eastern countries have successfully resisted.
This has done two things. First it has protected the Eastern countries from being overwhelmed by migrants that have no cultural connection to their potential host nations. Secondly it has begun to create a schism in the EU itself.
Most interestingly, the Eastern European countries that are tight on immigration are also friendlier to Israel. This is has helped black anti-Israel legislation in the EU.