For station cargo flights, Cygnus is an option, but it can’t bring anything back the way Cargo Dragon can.
Sierra Space’s Dreamchaser is another ISS cargo resupply option. The first one is already fully built and at Kennedy Space Center for launch this year. It doesn’t use a SpaceX rocket, and it also provides return cargo just like SpaceX Dragon does.
For manned missions, the only other option would be Boeing Starliner, and I don’t think anyone else is ready to call that operational.
Starliner isn’t the ONLY other option, but the other is REALLY EXPENSIVE. NASA’s Orion capsule is crew rated and could also dock at the ISS.
However the only current crew rated rocket to carry it right now would be the SLS rocket which is really built for deep space/lunar missions. Using it to fly to the ISS is very possible but would be VERY wasteful as far as money goes. So you’re mostly right, Starliner is the only other reasonable choice for crew flights to ISS for the USA.
Sierra Space’s Dreamchaser is another ISS cargo resupply option. The first one is already fully built and at Kennedy Space Center for launch this year. It doesn’t use a SpaceX rocket, and it also provides return cargo just like SpaceX Dragon does.
Starliner isn’t the ONLY other option, but the other is REALLY EXPENSIVE. NASA’s Orion capsule is crew rated and could also dock at the ISS.
However the only current crew rated rocket to carry it right now would be the SLS rocket which is really built for deep space/lunar missions. Using it to fly to the ISS is very possible but would be VERY wasteful as far as money goes. So you’re mostly right, Starliner is the only other reasonable choice for crew flights to ISS for the USA.