I'd be interested in knowing what percentage of the Hidden Champions are publicly traded companies. Companies of that size are very likely to be acquired in the US. Consolidation is a constant activity by many public firms and probably (I am speculating) tends to reduce the proportion of mid-tier companies relative to Germany.
Once acquired, these companies have an additional set of factors weighing on them in that the founding team is likely to leave, budgets are controlled by, and, profits are sent to an external firm. Those three factors will reduce the company's ability to determine it's own fate.
The term "Hidden Champions" though usually refers to "boring industry" companies like part suppliers, not actual manufacturers of consumer products.
Like the one company that practically has a monopoly on manufacturing the plastic part that goes on the end of flat roof drains -- not exactly something to write home about, but still a massively stable market creating plenty of jobs.
In the US, the big three automakers generally don't acquire small companies. A lot of work in the industry is done by companies like Delphi (who also have sites in Germany)
Once acquired, these companies have an additional set of factors weighing on them in that the founding team is likely to leave, budgets are controlled by, and, profits are sent to an external firm. Those three factors will reduce the company's ability to determine it's own fate.