“But, those groups assimilated.”
Whats to assimilate? You don’t have to leave your culture now. You don’t have to cut the strings to your home country. Speak Spanish, fine we will change our language requirements to match your needs. Watch English-ed based TV, no fear, we will give you Univision, Telemondo etc. Spanish newspapers and radio stations.
They haven’t left their old culture to develop a new culture in America, they just changed their location.
People were speaking Spanish in America long before they were speaking English.