The National Science Foundation is responsible for promoting basic research and education within science and engineering. Each year the NSF awards approximately 7 billion dollars in grants to American institutions.
The international activities of NSF are managed by the International Science and Engineering Section (ISE). A key programme is the Partnership for International Research and Education (PIRE), which promotes research collaborations with institutions abroad.
The National Institutes of Health is the largest research financier in the USA. It is predominantly active within the field of medicine. NIH comprises 27 institutions and centres, with its own research strategy and a focus on specific illness. Each year, the NIH awards more than 28 billion dollars and predominantly funds research at institutions in the USA, although it also offers funding to international projects. The Research Project Grant Program (R01) is one of the most common funding types available from the NIH and is open to international applicants. This is also the case for the Small Grant Program (R03), which provides funding for short projects (duration of up to two years) and pilot studies, etc.
Grants.gov is a joint website where you can find and apply for funds from various public sources of funding in the USA.