If you wait until you're 50ft from a junction before changing lanes in order to turn left and leave yourself no time to signal your intention to do so because you need to brake, then you need to look to your own positioning and bike handling.

The idea that you are exempt from signalling your intentions to other road users because you don't have the necessary skills to do so is, I'm afraid, risky.

If you have the usual US brake setup of right hand/rear brake, then signalling while braking isn't difficult. In any case, you should have signalled, moved into the left turn position and then braked.

My sympathies, such as they are, are with a driver who thought you might be going to do something, but wasn't sure what, since you weren't indicating your intentions