Definition of money laundering:
Money laundering is the process of illegally concealing the origin of money,[....]
Let's say the source of your funds are clean but do mixers make the process of concealing the funds' origin legal? I think this remains a grey area up to now. I haven't read any updates on the cases filed against owners of previously seized mixers prior to Chipmixer.
Mixers are not illegal, even when United States have strict rules that mixers can not abide to
Unfortunately, for centralized mixers at least, you're wrong. In the US, you're prohibited to run a non-regulated money transmitting service; and that's pretty much what a good Bitcoin mixer is. Anonymous and it involves and intermediary who will transmit money. However, that does not apply on every country, and it does not mean decentralized mixing is illegal.
This is certainly the bottom line. The US (as well as EU) will also define money laundering to be whatever they want it to be, even with the rest of world not quite in agreement. Generally, any unlicensed money transmitting service will be considered money laundering if there is no KYC in place, even if not really any different than going to a shop with "dirty cash" and getting change that's "clean" from a vendor.
There's that phrase that laws needs to be changed according to the changes in society. That's most likely what's happening with the changing definition and scope of existing laws.