Ron, you set up questions in a funny way...I'd have to spend most of my answer explaining why "enriched" is a loaded term and why finding some positive aspects of any "wave of immigration" does not necessarily demonstrate that the entire situation was generally benefical.

   When there was a large influx of immigrants from Costa Rica and Nicaragua after wars and disasters awhile back, we got quite a large number of criminals and social misfits among some perfectly decent folks....so were we 'enriched'? Does ONE nice, decent school teacher in a group of a bunch of former army death squad members mean we are enriched? See the problem? You can have all the 'enrichment' slogans you wish....we still need a way to sort out the decent school teacher from the others BEFORE they arrive here and fade into the shadows.

I saw prison officials explaining that about 90% of inmates in S. Cal. jails and prisons are affiliated with ethnic gangs of some sort...Latino, Black, White, Chinese etc....and now, even Russian..(though smaller in number). These groups cause enormous law enforcement problems just from fighting among themselves...not to mention preying on the populace in general. New immigrants, especially illegal ones, usually end up in neighborhoods where they cannot easily avoid the gang culture, and are often co-opted into criminal behavior when the promised jobs are not easy to find.

That is happening even as some others are 'enriching' us with the better aspects of their varied cultures.

You asked me if I could name any group which hadn't enriched us. I could ask YOU if there's any group which hasn't brought its share of problems. I repeat...we need to control the process, so as to minimize the problems and enjoy the enrichment.