Didn't they threaten to invade the Netherlands if they continue their investigation in US War Crimes ?

You are, I believe, referring to the "American Service Members Protection Act" [1], signed into law in 2002 by Bush?

This law, still on the books, theoretically allows the president to order military action against the ICC in Den Haag (The Hague) should they ever try an American Service Member.

> The act also prohibits U.S. military aid to countries that are party to the court. However, exceptions are allowed for aid to NATO members, major non-NATO allies, Taiwan, and countries that have entered into "Article 98 agreements", agreeing not to hand over U.S. nationals to the court.

[1]: https://en.wikipedia.org/wiki/American_Service-Members%27_Pr...

Nonetheless that does not make the US forces in Germany an occupational force.

> Nonetheless that does not make the US forces in Germany an occupational force.

A stick is a stick regardless of whether it has been used to thrash someone lately.

I put it in quotes in an attempt to highlight that it was not a formal military occupation. Their presence does show some level of influence the US military has and it is a threat to prevent Germany from making any truly radical moves.