Hi there, this is a good question. Credit is very important in the USA, but there is so many ways that you can improve your credit score, in that way you can asure a seller that you have the money to pay for what you want when you have the money. If you are young or just starting in this country you can start your credit asking your bank for a savings/credit card. This card works like a debit card but will give your the points to build your credit. Your credit limit will be the same amount of money that you will put in the card. So you put money and you can spend money. It's safe because the bank wont allow you to spend more than what you have like the credit cards. Another way to establish credit is with a big purchase like a car or a department store card. This is a little dangerous since is a big spend but if you are discipline and pay on time your credit will start rising. And last but not uncommon is paying rent or services with a credit card that has low interest. You must be very discipline with this method because one miss payment and it can ruin your rent history, but basically if you have the money for your rent or paying your services you can add it to your credit card (preferable one that gives you points) and pay of the credit card because you already have the money.
Like any investment in life there is certain levels of risk and you have to be very discipline to build up your credit and establish that trust when you want to buy something.
Good luck!!! and Be Discipline