They definitely were! The American steel industry invested maybe 1/3 of what the Japanese did in steel R&D through the 60s and 70s, were among the last producers to adopt basic oxygen furnaces and continuous casting.

A great report on the CC issue:
https://www.princeton.edu/~ota/disk3/1979/7902/7902.PDF https://twitter.com/sandypsj/status/1250171946991587331

That the geography of integrated mills changed relatively little from the turn of the 20th century to the 80s is relevant, too. River valley plants in PA and OH were great for getting materials in 1890, but sucked when modern production techniques required layout flexibility

They also made it more difficult for American mills to access high grade foreign ore from Brazil/Australia; it's no coincidence that the handful of modern mills in the US and many abroad are on harbors.

And then, of course, there's the issue of labor. US steel makers were very afraid of strikes, which eventually led them to agree to a slew of anticompetitive agreements that had the eventual effect of increasing labor costs/reducing flexibility.

(Agreements which took place without touching the industry's rich tapestry of scientific management-y labor practices, which had the dual effect of wasting institutional knowledge on the part of the unionized workforce and alienating the same)