America was built by immigrants after slaughtering the native indians so...
They were "slaughtering" each other before the white man came. Due to their constant wars they never did anything, nor build anything resembling a nation. Nations are built on conquests and wars, just in case you never read the history of every single nation that currently exists.
Built by immigrants. LEGAL immigrants. Immigrants whose arrival was recorded. Immigrants who were known by authorities to have entered the country. Try to differentiate between ILLEGAL and LEGAL immigration, libtard.