List of mobile network operators

United States

Networks

Coverage map (very optimistic) provided by OpenSignal. In general Verizon has the best coverage, followed by AT&T, T-Mobile, with Sprint far behind. Where I need it, Verizon works best.

List of MVNOs

• https://bestmvno.com
• https://wikivividly.com/wiki/List_of_United_States_mobile_virtual_network_operators

Austria

Networks

OpenSignal also provides a coverage map. As a general idea A1 has the best coverage, especially in rural areas, followed by Drei (slightly worse), and T-Mobile (not too bad).

List of MVNOs

See the LTE-Forum.