For the last 20 years NASA has intentionally run their Commercial Crew Program, which has the stated goal of developing/fostering/funding the development of commercial providers for launch vehicles.
They, by plan they explicitly laid out and implemented, decided to rely on American commercial providers. And that's what they got. And in doing so, the program ended up producing the most prolific/successful launch vehicle in history.
>> It's only through the miracle of the vanity of billionaires that there's even a realistic second choice (Blue Origin) that might develop
Yes, this is another company which the NASA commercial program explicitly funded in order to get them to develop another launch vehicle.