Poles were among the last waves of migrant groups from Europe to go to North America. Polish numbers certainly never reached those of other immigrant groups especially the English, Scots, Germans, Italians and Irish. Between the 19th and 20th century only a little over 1,000,000 Poles emigrated to North America which averages out to 100,000 a year. Compare that to today's non-EU migrants coming to Europe at a rate of over 1,000,000 per year rather than per century.
And as mentioned although Poles were quick to assimilate they were still subject to Polonophobia by both the established populations of non-Poles in America and Canada as well as by other first and second generation non-Polish immigrant groups.
Regarding the EU there are no limits on the free movement of labor among EU citizens. So it is incorrect to refer to Poles finding work in say Germany or the UK as being "mass migration". It is simply labor lawfully traveling and finding work within the common market place. No different than a Bavarian moving to Berlin to follow a career. No different than a Californian relocating to New York to take a new job. And Poles have been consistently and highly successful in competing in many countries due to the strong work ethic, professional skills, and multilingual abilities which we bring to the table.
There is no account of Polish immigration (in any numbers) to other countries resulting in spikes in crime, establishment of "no-go zones", or pervasive and intergenerational welfare dependency.
There is no account of Poles being racist while living, working or settling permanently abroad. Indeed, Poles have long been a vibrant thread in the tapestry of many mutlicultural, mutliethnic, multiracial societies.
Regarding the cultural marxist stooge Frau Merkel she may have found some loophole so she could invite the entire world to Germany in the hope of getting a Nobel prize in virtue signaling for herself. But even her cuckold electorate certainly haven't been happy about what she has been doing and the rest of the EU rightfully balked at the pathetic, desperate attempt of establishing migrant quotas following her idiotic, unaffordable and untenable decision. So now, with her career at stake, she has been trying to reverse course by ramming through legislation to enforce integration and begin deporting hundreds of thousands of fake asylum seekers. Such damage control fixes would never have been necessary if her open-door migration policy was ever truly legal to begin with.