In the past you could have made an argument about foreign airlines not being held to FAA standards.
But today, FAA knows exactly which jurisdictions regulate airlines to a comparable standard and which don’t. Denying cabotage and other higher rights to those airlines is 100%, as you say, naked protectionism.
There are some services (cloudfront for example) which require this region. Its not that much harder to have multiple regions in your deployment but putting everything in one is simpler for smaller startupy orgs.
It’s not required during an incident. The data for these services is globally replicated. It’s only if you need to make changes that you might be impacted if you’re already successfully operating out of another region.
Governments are good at pure science, research, and individual technologies. They are not good at making products. That is fundamentally where private companies have a massive advantage.
I believe that max demonstrated wave height will have more to do with the height of the hydrofoil than the wingspan / ground effect distance.
Having said that, I'm pretty sure the much larger Monarch (their further future 50-100pax model) will probably have longer vertical supports on the foils.