I think you did a good job acknowledging the challenges in comparison due to scale. The pairing of open borders and a welfare state, regardless of scale, removes the incentive for participation in work and decreases the value of the work by active participants since a fraction will be going to care for others. While the USD has plenty of help from the reserve's printing, this pairing is removing buying power at an even more accelerated rate and pushing more citizens toward the poverty line.

I consider it simplistic to label all immigrants as intentionally destructive or malicious, it is likely that many don't consider national implications of their immigration in comparison to their personal gain (clearly that is ignorant, but that is not the argument). A value-contributing immigrant won't ignore the opportunity to pursue happiness offered by open immigration.