Last time I checked, Iran was not known throughout the world as a leader in consumer wireless telecommunications.... The US has prepaid wireless on older or lower end phone models such as the note4. You can get brand new note4's in the US for under $200 without financing. AFAIK SIM cards don't cost anything. You go on the website of whatever carrier you selected and buy whatever calling and/or data plan you want to pay for. However most people that I know personally prefer "regular" post paid service. With or without a contract. Without contracts, you simply have to pay for your phone hardware up front. Again, AFAIK SIM cards are free. I've had mine replaced a couple times over the years and my carrier has never asked me to pay.What you're seeing in the US is aritifically inflated bubble aka scam. In the devolved countries where people don't get a credit without collateral (at a mere 0% APR 27.8% interest rate) and don't get to declare personal bankruptcy when they run out of money, it's usually a $10 SIM with access to all services: voice, data, whatever, at some per-minute and per-megabyte rates. And smartphones cost hundreds.
I pay T-Mobile about $100 a year, BTW, and can purchase a day of mobile data if I ever find the need for it in someplace without free WiFi. I'm not upgrading from my $200-from-fleebay Note 4 as it's the last one with easily replaceable battery, so the free with $700 commitment after paying $300 is of little interest to me.
I agree with you that the lack of a removable battery cover on some newer model devices is a negative thing. That has nothing to do with the US specifically. Some brands still have the feature in their newest products, others don't. Similar situation for SDHC storage slots. I'm sure you'll find that newer model phones (assuming such things are available) in Iran also lack this feature.
Some of our states are in the process of legislating a requirement that consumer electronics must have a user replaceable battery. It didn't occur to me until just now that such a law will likely affect dive computers as well. Unless such a law is enacted at the federal level, I believe it will cause consumers in those states to get Samsung and Apple brand phones mail-order only. Brick and mortar retailers will suffer, and consumers will have a minor inconvenience.