I'm not sure about that. For starters, it's easier to immigrate to Germany or the UK than to the US, and by percentage of the population, Germany does host a higher number of immigrants.
The US does accept more foreigners yearly, but it makes it a long way, if any, to stay in the country permanently.
Don’t take it from me, look at what the German government is doing with allowing foreigners to immigrate there. When a country throws open its doors the way Germany has, you must ask the question - why?
Someone born in France but lives in Germany vs someone born in New York but lives in California are both similarly easy from a legal standpoint. However counting the Frenchman in Germany as an immigrant seems kind of dubious given that's kind of the point of the EU.
For instance, the US has immigration quotas for pretty much everything, thus the backlogs that resulted in Chinese and Indian born people to wait for a decade or more to achieve their permanent residency status. The process is also extremely complex and, as a result of that, it is quite expensive, in the order of thousands of dollars.