This question is in part based on a premise that is between misleading and false.
In Germany schools do not choose to skip the whole my-tomatoes-for-your-cows lesson.
What is true is that there was usually not a big chunk in education dedicated to the columbian exchange exclusively. And the concept is so new for the slow moving German school system that the concept is still often named in its English, untranslated form: https://de.wikipedia.org/wiki/Columbian_Exchange
Both factors may be responsible for people you asked giving a dismissive answer. They usually do not recognise the name of the concept and it didn't feature that big during their school education.
But German school kids do know where potatoes, tomatoes, tobacco, maize and lots of other stuff they consume daily came from originally. This Kolumbus-Effekt has its part in modules called "Age of Exploration", "Age of European Expansion" and the like.
This can be shown by looking at the current curriculum for to-be-teachers:
European Expansion (until the End of the 18th Century) (Lecture)
The beginning of the European expansion overseas is in the historical memory until today primarily and to this day the perspective of the heroic explorer dominates, not that of the man who all too quickly drafted concepts for subjugating the indigenous population.
The history of European expansion oscillates between the fascination with the unknown and the transfer of knowledge about foreign cultures and plants, goods and techniques on the one hand, and the subjugation, violent proselytizing, exploitation and even extermination of foreign peoples on the other. On the basis of the Portuguese, Spanish, Dutch, French and English expansion up to the end of the 18. century, the lecture will take up different perspectives on European expansion and colonialism, not least the already contemporary problematization of colonial rule in ethical-religious as well as international legal discourses.... (further see Digicampus)
Modul GES-3022 (= FB-GsHs-UF-Ges 07-FNZ): Geschichte der Frühen Neuzeit: Übung und Vorlesung Freier Bereich (= Epochale Zusammenhänge und wissenschaftliches Arbeiten – Frühe Neuzeit) –– Modulhandbuch Freier Bereich im Lehramt an Mittelschulen LPO UA 2012 Lehramt, University of Augsburg 2015
In the same year this was also part of the first year curriculum for students becoming teachers (commercial link).
This is often mentioned en passant during German school kid education and in class 7 usually covered in all states (Bundesländer). (Federated education system is not uniform across the whole country).
This can also be shown by asking pupils above a certain age whether they know about the content of this concept. Ask about potatoes geographical origin and you usually get either the right answer or proof for a failing education system. Both outcomes are possible.
German schoolbooks are now almost famously bad, but a recent study in the department of schoolbook research comparing German and Mexican schoolbooks concluded that overall both leave quite a bit to desire.
It might be that some less well known plants are not all present with their origins. While anecdotal, the experience reported in the question is still a nice example of a failing school system and/or forgetfulness. They really should all know this, basically. The potato at least is always – as early as kindergarten – mentioned as coming from America, first used as an ornament, but essentially mistrusted as food. Then Prussian king Fritz II planted a highly guarded garden to lure the peasants into stealing the plant. Yes, this is another anecdote that is also essentially at odds with known dates of first cultivation. But it was indeed Friedrich who ordered planting potatos. Usually the anecdote and the real story are told in school:
In Prussia, Frederick II had great difficulty in getting the cultivation of potatoes accepted. On March 24, 1756, he issued a circular order to his officials and thus the first of the so-called potato orders with the order "to make them understand the benefits of planting this plant and to advise them to plant the potatoes as a very nutritious food before the end of this early year". It is said that Frederick II literally had his farmers beaten into potato happiness. It is sometimes described that the king achieved the desired success by having a potato field guarded by soldiers and thus tempted the farmers to steal the supposedly valuable plants for their own cultivation. Whether he really took this measure is not certain; in addition, this action is also attributed to Antoine Parmentier. (WP)
A recent master-thesis that covers this for historical textbooks used in Switzerland schools looks at Wilhelm Oechsli: "Lehrbuch für den Geschichtsunterricht in der Sekundarschule. Allgemeine und Vaterländische Geschichte. 2 Bände. Zürich: Verlag der Erziehungsdirektion: 1883. (Franziska Basler: "Darstellung Christoph Kolumbus’ in den Zürcher Geschichtslehrmitteln seit 1872. Heldenhafter Entdecker oder brutaler Eroberer?", Master-Thesis, PH Zürich, 2015.) Some of the assertions and conclusions in the old book might look of course quite horrendous today. But again, the content of this concept is covered in there.
One phenomenon left might then be that without having a Begriff – the "columbian exchange" – those asked may be unable to begreifen (~to grasp) what is being talked about.
As the focus seems to be mostly on plants (in schools, as shown above) I'll bet the farm that with most Germans quite an interesting conversation could be held whether the horse went either to or came from America. Karl May and Hollywood had much more influence on knowledge about that than any schoolbook.
