The whole point of bitcoin was to create a cryptocurrency which did not needed a third party for your transactions to go through, relying on a centralized exchange goes against bitcoin's nature, however I understand that it is inevitable to use them if you want to be a trader or an investor, so what you can do?
To transact you still do not need a third party, if you want to purchase you need to go to the exchanges or find a seller and exchanges are the safest option rather than trusting a random seller and hence it is not against bitcoin's nature.
@OP, you can trust the top exchanges which are registered in the US because they need to comply with the rules and most probably will not run away, coinbase can be trusted and as suggested by many, never keep the coins in any exchanges if you are not trading.