I wouldn't call commercial stations in other countries more "adventurous" necessarily. Most commercial radio stations in Canada are owned by Bell, Rogers, Corus, etc., and Bell's Bounce Radio (adult and hits) and Move (AC) have fairly tight playlists.
In fact, most North American ACs and Hot ACs tend to be less uptempo / more "pop rock"-friendly compared to the equivalents in other countries. For example, Dubai 92
sticks to familiarity, yet the station is not
overloaded with Taylor Swift and Katy Perry like many American ACs. Nor do they frequently play "filler" like Sara Bareilles or Ingrid Michaelson. Dubai 92 is not afraid of playing rap or R&B, provided the songs played are hits, yet they also play some older 80s/90s ballads. Also, AC stations that are more rhythmic-friendly than the average American AC include Heart in the UK, Kfm in Cape Town, and 104.6 RTL in Berlin, just to name a few.
So the "play it safe" mantra is probably perceived by the less rhythmic sound in the US, and not as much of the playlist being "wide". Remember, most commercial stations do not program similarly to a station like BBC Radio 2.