Anyone have a good way to mitigate?

Found a huge swarm of ants today congregated near my door. Most were winged, when I examined them I saw that they were not termites but ants. It looked like they were concentrated near the threshold of our door and near a split in the OSB siding that "meets" the foundation. We have a big concrete steps leading to our front door, basically a big block of concrete with steps molded. The builder did not seal the gap and the block of steps has seperated a bit away from the foundation leaving a gap where the ants have crawled in and around.

Unfortunately I don't know what kind of ants these are but I suspect them to be cornfield or moisture ants as they have a brown appearance. However, that is not good as it means I have rotting wood somewhere. I think it's likely that the rotting wood is the siding itself as the bottom part of the OSB has gotten soaked with water from heavy rain and watering of plants. I've moved the plants away from door and have sprayed the crack and the ants with the complete insect killer from Bayer. I bought some silicone caulk which I will seal the gap as best I can.

My real concern is if they have done any damage to any siding or have gotten into the crawl space. I know an inspection may be needed but I hope that they don't have to demo the concrete block of steps. I think I may be overthinking this though, I believe it may just be the rotting OSB/wood near the threshold and not necessarily any other structure damage/rot.