Suing companies is much harder than Internet comment sections imply. You would need an airtight case for any reasonable lawyer to proceed with such a case. From your post, you don’t appear to have any smoking gun evidence that they declined you due to marital status. You can’t win a lawsuit based on a hunch.
Contrary to popular belief, it’s not necessarily illegal to ask candidates about their marital status in the US. It would, however, be illegal if they used the answer to this question in a way that influenced their hiring decision. Frankly, it’s more likely that they were playing the “getting to know you” game with some poorly-advised small talk.
Before you consider suing, ask yourself what you expect to achieve: If you want an easy payout, remember that your lawyers will take a significant amount of anything you receive. If you lose, are you prepared to pay the legal fees yourself? Your lawyers won’t work for free and suing a company is an easy way to accumulate huge legal fees.