You won't lose the apps you have installed but
1. They won't update until you switch back so you'll likely need to switch 2 to 4 times a year as your bank and/or other services deprecates their old apps.
2. Switching requires manually re-entering your name, address, phone number, and credit card info every time.
3. Any subscriptions you have via Apple Pay will be cancelled.
Thanks Apple!
And note: While the average person does not have bank accounts in 2 countries I've run into plenty of apps I needed as a tourist that are only available on that country's store. For example the Lime app is not available in the Japanese store because Lime isn't in Japan but if I'm visiting a country with Lime then I want to be able to use the Lime app so I need to switch stores.
Meanwhile my Switch lets me have multiple user accounts. Each user's account can be assigned to a different country so I can buy The Touryst from the USA store and Japan exclusives from the Japan store. (not saying 2 accounts are the best solution it's just surprising that a Nintendo device does this part better than Apple)
It is not reasonable for Apple to make using the phone in more than one country so hard. That is something Apple has the easy power to fix.
I am in the market for a video chat device usable for people in the age of 70+. This device is perfect.
There is no real reason to limit it to a region but they do. Plug adapters are easy to come by and one place I saw a spec which said 100-240V 50/60Hz for the power adapter. But marketing/shipping/support/multiple SKUs might want them to limit distribution. But they are not up-front about it.
And you do not figure out until you are ready to order.
It should be obvious to put a prominent note on the landing page that the product only is available in select locations. Especially for a global brand.
The US has approximately zero laws dealing with privacy. I'd bet a lot of money on that being the real reason.