This article would have more weight if the United States were a signatory of the Mine Ban Treaty. It is not. Thus we have a typical case of the US urging others to do something it is quite unprepared to do itself. Does that not strike you, gentle reader, as just a tiny bit hypocritical?

can domestic terrorists get these kinds of devices?

I've always felt ambivalent about mines - once upon a time, very far away, I set claymores out every night and slept better for it. Minefields help keep troops alive - they also kill the innocent in future times. Here is a list of "States not party to the Mine Ban Treaty include: China, Egypt, India, Israel, Pakistan, Russia and the United States." "Cluster" weapons have similar issues and the US military is trying to create a better warhead with a lower failure rate (current weapons fail a lot). Mines and shells and bombs from wars all the way back to the Civil War are found in the US and in Europe as well. The only cure is to quit having wars.

Do U.S. weapons companies make and sell land mines?

Considering that the United States, Russia, and China (all major drivers of global conflict and sources of weaponry) have all refused to sign the Mine Ban Treaty, it's hard to call it very successful.