I fear it will be limited. AF can't "offer" lounge access when frequent flyers need to spend thousands of dollars to get to Elite Status.
By the way, the "regular" Platinum card is very cheap in the US ($450). Here in France, the annual fee is 520 € (roughly $775).
Regarding the KLM Platinum Amex... I can't find anything about it on both the KLM and the Amex NL sites.