My assignment answers show similarities to my friends', though they differ in content. Can I be accused of plagiarism?
Well, it isn't a problem until it's a problem, so don't panic.
But, there might be explanations that account for it. They are your friends, so you may have developed similar speech patterns that make the same phrasing natural for all of you. You are in the same class so you might have picked up the phrasing from the professor and used it in the same context. Or from a textbook.
But the key is that the answers are different. I doubt that it will become a problem. If you are called on it and didn't cheat/coordinate, then saying that you can't account for it is accurate. It is doubtful that if you did cheat/coordinate that this would be how your coordinated. Relax.