1. Integrated Taxonomic Information System (ITIS): ITIS is a collaborative project among several US and international agencies, and it provides a comprehensive database of scientific names and taxonomic information for all living organisms. It includes information on species found in the United States, as well as their scientific classification, distribution, and common names.
2. The National Audubon Society: The National Audubon Society is a non-profit organization dedicated to the conservation of birds and their habitats. Their website includes a comprehensive list of bird species found in the United States, with information on their range, migration patterns, and conservation status.
3. The Nature Conservancy: The Nature Conservancy is a non-profit organization dedicated to protecting and conserving natural habitats. Their website includes information on many animal species found in the United States, including mammals, birds, reptiles, amphibians, and fish.
4. The Smithsonian Institution: The Smithsonian Institution is a group of museums and research centers dedicated to the increase and diffusion of knowledge. Their website includes information on many animal species found in the United States, including exhibits and collections from various museums.
5. Local Biodiversity Databases: Many states, counties, and regions have their own biodiversity databases that provide information on local flora and fauna. These databases can be a valuable resource for finding information on animal species found in specific areas within the US.
It's important to note that due to the vast diversity and abundance of animal species in the US, it's not feasible to provide an exhaustive list here. These resources should provide a good starting point for exploring the wide range of animals found in the country.