So what is this "Clovis Barrier"? It's the idea that there were no people here in the Western Hemisphere before Clovis arose. Even today, some archaeologists absolutely reject the idea that there were any people here in the Western Hemisphere prior to about 13,000 years ago. Their reasoning is that there is just no hard evidence for a discernible culture prior to that point. However, there are a few sites that challenge this notion. Meadowcroft in Pennsylvania, Monte Verde in Chile, the Topper Site in South Carolina, and now Buttermilk Creek in Texas, all purport to contain pre-Clovis stratigraphic levels and artifacts.
Both sides of the debate have valid points. Those who reject pre-Clovis cite the seeming invisibility of these hypothetical pre-Clovis groups within the landscape. Where are the identifiable tool types, they ask? Where are the sites? Those who accept pre-Clovis point out that linguistic and DNA evidence now both support the idea that people entered the Western Hemisphere as early as 25,000 years ago, before the height of the last glacial maximum (LGM, in paleo-climatological speak, also known as Marine Isotope Stage 2, or MIS 2). We know that sites as old as 30,000 years have been found in Siberia, although it is open for debate about whether or not those were inhabited by modern humans, or Neandertals. And there's ample debate about exactly how people made their way into North America, and onward to South America, as well as how quickly.
While the Buttermilk Creek site may have settled the question for many, much more work on this question will have to be done. For example, if these people did not hunt big game using massive spear points, what did they do for a living instead? If the coastal migration model is correct, then maybe they fished - how visible will these activities be, archaeologically speak? Maybe people used multiple routes, both inland and coastal, to colonize this hemisphere. If so, the archaeological imprints of their activities will be varied accordingly. In summation, this issue isn't likely to become less complicated anytime soon.