Vector data has a much smaller footprint in most cases, but takes lots of processing to render, and even more if you need to be able to zoom around the map. Rendering the US down to z17 as raster tiles allows for efficient processing, but could easily get into 10s of GB (which makes sense, since it is creating thousands and thousands of png images). The size grows exponentially with each zoom level though, so if you only need something like z12, you might be able get it into the 10s of MB range.