Why is there a difference in the adoption of "Kindergarten" in American and British English?

As someone living in the US, I've heard the term "Kindergarten" used quite frequently. However someone from the UK was mentioning to me that the term is really not used that much in British English. Looking at the Wikipedia article on Kindergarten it states:

In British English, nursery or playgroup is the usual term for preschool education, and kindergarten is rarely used, except in the context of special approaches to education, such as Steiner-Waldorf education (the educational philosophy of which was founded by Rudolf Steiner).

I'd like to know why this variation in adoption exists.

Kindergarten was brought to the United States and the UK by German sisters Margarethe and Bertha Schurz.

In 1856 Margarethe Schurz started a kindergarten in the Schurz's Watertown home for her young daughter and four of her daughter's cousins. When more children wanted to join, Mrs. Schurz opened a school in this small building. This was the first kindergarten in America.

While living in Germany, sixteen year old Margarethe had been influenced by a series of lectures by the noted educator Friedrich Froebel. Froebel's course was on the "the new education," of which kindergarten was the first step. She later assisted her sister, Madame Ronge, in running a kindergarten in London. After moving to Wisconsin in 1856, Margarethe Schurz applied these ideas to her school.

Wisconsin History

I couldn't find any relevant research relating to the prevalence of the word Kindergarten in the United States versus it's relative rarity in the UK, however I imagine it has to do with wide-spread German immigration to the United States during the 1800s.

The concept of kindergarten was popularized by noted education reformer and congressman Horace Mann, a champion of public schooling who looked favorably at reforms in the Prussia of his day. He also explained the garden metaphor:

Kindergarten means a garden of children, and Froebel, the inventor of it, or rather, as he would prefer to express it, the discoverer of the method of Nature, meant to symbolize by the name the spirit and plan of treatment. How does the gardener treat his plants? He studies their individual natures, and puts them into such circumstances of soil and atmosphere as enable them to grow, flower, and bring forth fruit,-- also to renew their manifestation year after year. [Mann, Horace, and Elizabeth P. Peabody, "Moral Culture of Infancy and Kindergarten Guide," Boston, 1863]