The heavy flow of immigrants from Europe during the seventeenth and eighteenth centuries would likely continued had the 13 colonies remained under the control of London. The fate of the Louisiana territory is more problematical. For one thing, the Quebec Act of 1774 awarded to Quebec the region north of the Ohio River comprising modern-day Ohio, Indiana, Illinois and Michigan. Had this arrangement continued, this region would soon become French-speaking and would likely hinder westward expansion from the English colonies.
The Louisiana territory might also have remained Spanish, and it, as well as much of what is now the western US might have eventually filled up with Spanish-speakers.
Speaking of immigrants, had we stayed a colony of England, would slavery have been outlawed and N American slaves freed in 1807 as it was in England?
How would that have affected our present society? No Civil War?