Yes, it can. Marriage equality is banned in most states’ constitutions. The state bans are currently unenforceable and marriage equality is legal across the board thanks to a Supreme Court ruling 10 years ago, which me and boot man were discussing. He doesn’t think they want to bother to reverse it, even though some of the justices themselves have written clearly that they do and that’s the goal of their beliefs and platform.
If that were to happen, there is a federal law that would kick in called respect for marriage act, and places marriage equality back to the states, but they must honor a marriage in another state, even same sex marriages. This law will be challenged most likely and lawsuits are in the works.
So, if the 2015 court ruling is reversed and the respect for marriage act struck down, that leaves just a handful of states where marriage equality is legal, and could only be performed. The next step they would ban it all together at the federal level and reinstate marriage law is only opposite sex couples.
This is a very realistic scenario.
The best thing we have here in the US at federal level is respect for marriage act. It repealed definition of marriage of only to opposite sex couples and protects marriage benefits for same sex couples at federal level. It can also be put into the US federal constitution, but it would need to clear the hurdle of passing being passed by both houses of our congress then pass 3/4 states legislatures to be ratified. It’s very unlikely.