USA was once a united people

People sometimes say that USA was founded on an idea, as opposed to being a cohesive people.

Consider The Federalist No. 2:

With equal pleasure I have as often taken notice that Providence has been pleased to give this one connected country to one united people -- a people descended from the same ancestors, speaking the same language, professing the same religion, attached to the same principles of government, very similar in their manners and customs, and who, by their joint counsels, arms, and efforts, fighting side by side throughout a long and bloody war, have nobly established general liberty and independence.

This country and this people seem to have been made for each other, and it appears as if it was the design of Providence, that an inheritance so proper and convenient for a band of brethren, united to each other by the strongest ties, should never be split into a number of unsocial, jealous, and alien sovereignties.

Similar sentiments have hitherto prevailed among all orders and denominations of men among us. To all general purposes we have uniformly been one people each individual citizen everywhere enjoying the same national rights, privileges, and protection. As a nation we have made peace and war; as a nation we have vanquished our common enemies; as a nation we have formed alliances, and made treaties, and entered into various compacts and conventions with foreign states.

Obviously John Jay was referred to those descended from English settlers, and not Indians or African slaves.

Immigration is splitting America in a way that John Jay said should never be done.