Well let's see... You began this exchange by saying:
100 years ago, the US took a break from immigration — and America thrived...
So you were referring to the restrictive Immigration Act of 1924, but didn't use its name. Naturally some have different views of the necessity for, and results of, passage of the Act. However, we know that the '20s were when the U.S. began to veer toward isolationism. That continued through the '30s. Remember the ship carrying thousands of Jews trying to escape Hitler's Germany? The one turned away at Miami? Those people were sent back to Germany, where most died in Nazi concentration camps.
We are a nation of immigrants.
Oh, and I said in closing:
Again, read the Wikipedia article, which is only a starting point for anyone actually interested in all this.
Why did you repeat it as if it were coming from you?