I know my Light & Motion Urban 500 appears brighter than it really is and has a lot of spill because I've heard drivers and pedestrians comment on how bright it is. Monday a guy loading his car trunk as I passed said he thought I was on a motorcycle because the light was so bright -- and that was on the medium setting, around 250 lumens, far dimmer than an actual motorcycle headlight. But he noticed the relative intensity of the center spotlight beam.
But in the US I'm more concerned about being noticed, not by being polite. Unless you've spent a lot of time cycling in the US, particularly in states where laws are very lax for drivers, you have no idea how indifferent and even hostile many drivers are toward pedestrians and cyclists.
Literally, the easiest way to get away with murder in the US is to run over a pedestrian or cyclist and claim "They came out of nowhere! I never saw them!" Unless there is contradictory evidence from witnesses, video, etc., most law enforcement agencies will accept driver statements at face value. If the news media report it at all, they'll mention whether the cyclist wore a helmet, or had functioning brakes. But they won't mention driver negligence or culpability.
I'll worry about my lights after the US changes from this paradigm that pits hostile and indifferent drivers against human lives.
And even with bright and flashing lights and hi-viz colors, that stuff works only if the drivers look or give a damn. I was nearly hit twice Monday, while running bright daytime lights, and wearing hi-viz colors. The first was an Amazon driver who never looked up while turning from a side road into my path. The second was a woman who looked directly at me, made eye contact, then pulled into my path anyway and shrugged indifferently when I yelled and cussed.
Same with the driver who struck me in 2018. She never even looked up from her phone when she turned into my path. The lights, etc., made zero difference. And even with a police witness she wasn't cited for recklessness or negligence.
That's pretty common here, and nothing will change until drivers are forced to change.
If anything, I'm inclined to get brighter and more annoying lights. I'll dim them and lower the beams for cyclists and pedestrians on the MUP. But not for drivers. Not until the laws change regarding training and personal liability for negligent drivers.