I have ridden in non-motorcycle boots: hiking boots, Matterhorn combat boots (similar to Danners Ft. Lewis)-- they work well for riding, and are more comfortable than moto boots to walk in.
BUT, I have crashed twice on the street wearing moto boots (a Gaerne sport-touring type boot) --they work great for crashing
1. 40 mph low-side, right foot was pinned under the bike briefly and the ankle and toe protectors on the boots kept me safe.
2. Hit at a busy intersection by a clueless cager. Took the bulk of the impact on the shin protector (and the knee pad of my 'stich RC), again with no injuries.
So, for me yes, moto boots are important.
If you need a custom boot to accomodate your needs/size...the Vendrammini option seems to be the most protective.
Another option to consider (since you were asking about custom made in the US boots), perhaps, is getting a pair of Wesco's made to order. Their boots are very beefy (you can get them with toe caps and and double steel shanks) and would only be lacking in ankle protection if you supplemented with some stap-on style shin guards.
Wildlife Biologist for Hire!