If you are invited to someone's house for dinner in the United States, it is customary to bring a gift such as a bunch of flowers or a box of chocolates. If you give your host a gift, he/she may open it in front of you as it is considered polite. It shows that the host is excited about receiving the gift and wants to show his/her appreciation to you immediately. Even if the host doesn't like the gift, he/she will tell a "white lie" and say how much they like the gift to prevent the guest from feeling bad.
It is important to arrive at the expected time when invited to someone's house for dinner in the United States. Arriving too early or too late is generally seen as potentially inconvenient and rude, as the host may not be ready to receive guests yet.