foreign cars already have L5?

Nope and none are anywhere close. Such a thing, if it ever were to occur, would be a fractionally self-aware sentient computer that had situational and context sensitive awareness on an actively changing 3D environment, demonstrating real time learning of abstract concepts within 700 milliseconds.

Where is the sauce that we are 5-15 years away from level 5?

I'm referencing my experience here, as I have a masters degree in CS and ML around image processing. I follow Andrej Karpathy's progress very closely and read his whitepapers and monitor the massive progress made in the last 7 years by super-tuning 10 layer convolutional neural nets on the now petabytes of driving data, using his 8 Titan X GPU on his personal rig, and datacenters to use gradient descent to find models that distill the correct action given every possible environment, but they're hitting up against the limits of this technology. It's still just stacks of if/then statements, and in my opinion, they need to come to grips with reality and geofence their self driving technology and super tune a neural net for each and every 1 mile stretch of road, requiring cars to buffer a new model as you go, or else keep kicking the can down the road every few years on FSD in the pursuit of a situationally context sensitive self-aware cybernetic individual. Which is about 15 years away in my opinion, optimistically. We want this tech to be 15 years out, because after that nut is cracked, all other jobs are going away in a fucking jiffy. As computers with 3d situational awareness will eliminate 99% of all jobs.

I thought we would be achieving level 4 by EOY?

You are a very gullible person, defer such judgments to someone else you trust, to do such projections for you, ie, me.