I have never seen metal detectors in any bank in the U.S., and I have lived in the U.S. almost all my life. If there is any security at all in a bank, it usually just consists of a lone security guard—and then only in some larger banks and some areas. So, to answer your question, one usually is required to go through no security checks of any kind to enter bank. I have certainly never seen security at the level one sees in Italy. The gun laws vary from state to state on whether you can enter a bank with a gun, but “concealed carry laws” seem to allow this in increasingly more states. I think you are correct in stating the many Americans would not like to see the type of security you have in Italy, in part because of the view of many Americans about their right to bear arms, but also in part because most Americans would find it unnecessary and burdensome. Frankly, I think most banks would find such security to be unnecessary. For a variety of reasons, bank robberies are not all that common anymore, and “softer” targets like liquor stores with lots of cash seem to be “hit” more. By the way, I recently watched a fairly new movie about bank robberies called “Hell or High Water.” If you haven’t seen it, I strongly recommend it. It stars Jeff Bridges and was nominated for several various awards. There is one scene towards the end of the movie that demonstrates why some Americans may believe that bank security is not necessary in the U.S.!

No. It is not common place to have to go through a metal detector to enter a bank in the USA. But there usually are many security features. For example: The tellers often work behind protective glass. So to get money, you talk to the teller through a window, or sometimes even an intercom, and pass things to each other through a sliding box, tray, or a very small hole a few inches wide. There is sometimes an emergency shutter. If a bank employee feels threatened they can press a button and the shutters comes down closing the bank (and possibly injuring somebody at the teller's desk). Some banks have warnings about sensors that can trigger these shutters to close, if you have a camera flash, make a fast movement towards an employee door/window or something. There are usually many codes and swipe passes to move around a bank. Customers tend to be in a front room, and maybe a second layer room to talk to managers or make large deposits etc. But the employees handling money will be often another layer removed again. Another security feature is a safe that can only accept money. So any money deposited through the day can not easily be stolen, because you will need multiple keys, codes any sometimes have to wait for a 1 or 2 hour window each day when keys will work to open the deposit safe. And some banks these days are really just computers, where the teller needs to enter a bank account number and get a customer card, password and electronic authorization to then have a money dispenser spit out the requested money. A gun would be useless as the teller actually has no way to access money without a valid customer id.