Tesla Supercharger vs. 3rd Party Charging networks
Many EV enthusiasts believe that companies like GM should be funding EV infrastructure. However there are many who don't agree. After all when the first gasoline vehicles hit road vehicle manufacturers of the day didn't fund gasoline infrastructure. Gasoline infrastructure was largely funded privately by the fossil fuel industry and other interests.
Standard Charging System
Almost all car manufacturers with the exception of a few out of Japan have backed the near universal CCS (Combined Charging System). This standard was developed by a consensus of vehicle manufacturers through the Society of Automotive Engineers. Of which even Tesla is party to the development of this standard. CCS was developed later than Tesla's supercharger system or the Japanese CHAdeMO standard and hence charging networks using CCS have had a late start. But due to investments by private companies, public-private partnerships (some forced like the VW settlement) and in some cases fully publicly funded CCS charging stations, there have been stations popping up very quickly. So quickly that the number CCS plugs are now approaching that of Tesla's even with Tesla's recent rapid expansion in response to the Model 3 launch.
Tesla's Supercharging Network
In the early days of the supercharger network Tesla appeared to be working to build a network that connected dots on a map. They seemed out to answer the question “can I drive an EV to [insert remote part of mid-western US state here]”. This made a network that looked good on a map and helped make EV adoption look possible. However this also made some supercharging stations in high demand area's overcrowded and some supercharging stations in more remote regions see very little traffic. Tesla appears to be working to resolve this and are now adding larger multi-stall stations in high demand locations. But continue to be very determined to reach all nooks and crannies in all regions where Tesla's are sold regardless if demand is there for some of these stations or not. At least yet.
3rd Party Charging Networks
3rd party EV infrastructure seems to have been built mostly on a supply and demand basis (with the exception of some publicly funded projects). Organizations like Chargepoint, EVgo and Greenlots are all trying to make viable business models on providing EV charging solutions to customers. This has made area's with a high density of EV adoption havens for 3rd party EV infrastructure while remote area's with low EV adoption often have no 3rd party EV infrastructure at all. Though as EV adoption accelerates this should resolve itself.
Even today if I think about the longest road trips I've ever taken in my life the 3rd party infrastructure is already in place to make a vehicle with a range like the Bolt EV viable. The infrastructure exists today for someone like me to drive a car like the Bolt EV from Ontario, Canada all the way to Orlando, Florida and back again. And despite the lower available charging power at currently installed CCS stations the Bolt EV would only take a few hours (10%) longer to complete this journey than the original Model S 60 today. So the CCS charging standard has come a long way in a short time.
EV Charging Speed
Speaking of charging speeds CCS charge stations today are mostly limited to 50 or even 25KW charge rates (there are some in Europe that are 100KW). While Tesla superchargers have capacities of up to 145KW. On the surface this sounds like a charging network that is nearly three times faster than CCS. However even though the capability is there that doesn't mean that all EV's can use it. Most Teslas today cannot fully utilize 145KW. And the ones that can will only do so for a small portion of their battery state of charge. DC fast charging doesn't happen at a constant rate. Batteries can accept a higher charge rate when the battery charge is fairly low and slow their charge rate as their state of charge increases.