You can start with Coinbase as the US is one of the supported countries and you can link your debit card to make deposits.
AFAIK it's a safe exchange with good reputation. At least I haven't seen any valid scam accusation against them.
All the bad reviews I've read were complaints about their bad customer service which is not very responsive.
Besides there is this:
Coinbase reported a few years ago that the company verifying their kyc info was selling it on and they had to switch.
There are many good exchanges and the first thing you should check is if they support your country because if they don't your account will be locked and you wouldn't be able to withdraw your money.