Can base maps be updated?
The National Water Information System Mapper (http://maps.waterdata.usgs.gov/mapper/index.html) and related mapping functions use ArcGIS Map Services (http://www.esri.com/software/arcgis/arcgis-online-map-and-geoservices/map-services), so any additions to those maps must be done by the service provider. The USA topographic maps provided by ESRI and other commercial organizations are generally based on USGS topographic mapping, but they may have been enhanced or modified, and USGS has no control over the presentation or update of those map layers.
USGS completed the original 7.5-minute mapping of the USA in 1992, with more than 55,000 maps produced. These were all paper maps, and subsequently most mapping by the USGS and most other mapping organizations has shifted to digital products, including any revisions or updates to maps. As government resources for mapping have been reduced and a commercial market has arisen, many mapping activities have shifted to the commercial sector, particularly specialized applications such as adding local information. In some cases, the commercial operations may want to add other data, but in some cases not. For example, ESRI(*) mentions a Community Maps Program on their web pages that may be able to meet your needs (http://www.esri.com/software/arcgis/community-maps-program). Also, USGS has a pilot program to use citizen input to update the National Map (http://nationalmap.gov/TheNationalMapCorps/index.html), but there is no certainty that the commercial sources will adopt every feature on the National Map.
-----
(*) USGS does not recommend or endorse any commercial products, and mention of any specific products is for information only.