Let me cite some numbers:
https://www.migrationpolicy.org/article/frequently-requested... "According to estimates from the 2013 ACS, the U.S. immigrant population stood at more than 41.3 million, or 13 percent, of the total U.S. population of 316.1 million. Between 2012 and 2013, the foreign-born population increased by about 523,000, or 1.3 percent."
According to https://www.usatoday.com/story/news/world/2017/01/11/germany... the "mass immigration" to Germany in 2015 was about 890k, which with a baseline population of about 82 Million is less than 1.1%. And that was the peak, and has radically declined since then.
I don't have any numbers present right now, but I'm pretty certain that mass shootings in the USA have a higher death toll per capita than terrorism in western Europe.
Update: According to [1] the US has 30 death per 10k population per year from mass shootings. [2] finds 22 death from terrorism in Germany in 2016 noteworthy high, which equates to ... well, you don't even have to do the math to see how much lower it is.
[1] http://www.bbc.com/news/world-us-canada-34996604 [2] http://www.dailymail.co.uk/news/article-4052696/Germany-s-ye...