Before I put my own opinion, I would also wonder what you think of “European” style playing… I don’t know many American to bassoon players as acquaintances, however from what I hear from the recordings, the American bassoonists tend to have a timbre close to that of an oboe’s. Or rather of a cor anglais. It might have something to do with a different reed shape or scraping, or a different style of diaphragm technique.
Also, it is my personal opinion that I find the usage of vibrato much more uniform across the whole playing in American performers, while I observe the European players use vibrato in a varying manner, according to the phrasing, or don’t use vibrato at all in certain passages.
I would be happy if you reflect your thoughts on the matter too
All the best,