Of course, new archaeological sites are always being discovered, and recently a site just north of Austin, Texas - called the Buttermilk Creek Complex- revealed a cache of pre-Clovis tools dated 13,200 - 15,500 years old.
Clovis tools (on the left) are recognizable for their distinct laurel-leaf shape and fluting on both sides. The pre-Clovis tools from Buttermilk Creek (on the right) are a demonstrably different style.
Pre-Clovis sites are rare and difficult to confirm. We can imagine that early inhabitants of the Americas were nomadic, and weren't building houses or other features that would impact the landscape and survive in the archaeological record. Many archaeologists and specialists in related fields are still resistant to the idea of pre-Clovis cultures existing at all, since they complicate the long-standing Bering Land Bridge hypothesis for the peopling of the Americas. There is only a brief window of time when the Land Bridge was exposed and not covered in glaciers, so pre-Clovis people must have traveled by an alternative route earlier than ~12,000 years ago, perhaps by boat.
Some people suggest that sites like Monte Verde, Chile are contaminated with organic materials that falsify dating techniques. However, pre-Clovis culture may soon become an archaeological fact rather than theory as the number of sites grows. (LINK TO ARTICLE)