The Spending Explorer lets you explore the entire federal budget in increasing granularity, illustrating how awards derive from federal accounts. Interactive visualizations provide help building context, and multiple breakdowns clarify the relationships between federal-spending components. Agency profiles are offered so you can deep dive into spending by each Federal agency.
The resource features an API for developers, a wealth of data and tools, and additionally, the entire database can be downloaded for further research and analysis. A great starting point is the data lab, just go right there! https://datalab.usaspending.gov/
Spending.gov is a hidden gem and you can find it at https://www.usaspending.gov