From that same website you sourced:

What are the rates of literacy in the United States?

Four in five U.S. adults (79 percent) have English literacy skills sufficient to complete tasks that require comparing and contrasting information, paraphrasing, or making low-level inferences—literacy skills at level 2 or above in PIAAC (OECD 2013). In contrast, one in five U.S. adults (21 percent) has difficulty completing these tasks (figure 1). This translates into 43.0 million U.S. adults who possess low literacy skills: 26.5 million at level 1 and 8.4 million below level 1, while 8.2 million could not participate in PIAAC’s background survey either because of a language barrier or a cognitive or physical inability to be interviewed. These adults who were unable to participate are categorized as having low English literacy skills, as is done in international reports (OECD 2013), although no direct assessment of their skills is available.

Even if you take away non-native English speakers based on the numbers on that website further down (which you also quote), that results in a literacy rate of 86%. My point still stands that Taiwan has a much higher literacy rate.

Edit: formatting