"The safety of a republic depends essentially on the energy of a common national sentiment; on a uniformity of principles and habits."
The people you quoted (the Founders) wanted all people to assimilate, but there were a lot of walls put up for people who CAME like the Irish and the Chinese. For some people BROUGHT here it was illegal for them to assimilate: e.g. slaves. Washington, Jefferson, and Madison actually owned slaves which (who?) could not assimilate and become citizens - regardless of what those three wrote.