There was often active recruitment over in Europe and of course, there were no controls over how many poor people from Europe poured in every year. Conditions for labor would have been significantly better in the US had the inflow been slower/more controlled. As it was, the flood of immigrants really strengthened the hand of corporations over workers then just as it does now.
You’re right. The minor quibble was about the term ‘imported’. “Recruited” works for me - and shows freedom of choice on the part of workers coming here.