I suppose it all comes down to what you want this country to look like in the future. If you have no issue with an America that has over 400 million people - over half not of European descent - you will be pleased. If that idea is unsettling it is time to stop massive immigration.
When are we allowed to stop cheering for more immigration? When the percentage of whites drops to 50%? 25%? A majority white America already has laws that discriminate in favor of minorities; many of those minorities now consider such treatment equality; makes me wonder what they will insist upon in the new America that you seem to be eagerly heralding.
I hate to tell you this, but many hispanics are white.
The United States becoming more brown and more Roman Catholic doesn't bother me in the least. Why should it?
All the gains minorities have made in the last century will apply to whites if they ever become a minority.
You should really think about what you just said.