Since tax laws are very complicated, the article did not specify what exactly about our tax laws that prevent companies from bringing cash onto their balance sheet; but what we do know is that, the main reason why companies are borrowing instead of liquidating their foreign securities and bring the funds onshore, is because the US has one of the most highest tax rate for foreign investments in the world. Large companies, who hold investments globally, are already being hit with the foreign taxes; if they were to cash out and bring the proceeds to the US, they would have to pay another large tax bill to the government before even touching the funds. For this reason, the companies prefer to leave their investments oversea, and capitalize on its growth rather than taking it home and being able to use most of it.
A surprising fact stated in the article was that the United States is the one country that has the highest tax rate charged to its home