Your four links show zero cases of the US supporting Al Nusra. One's talking about how in the chaos the lines between groups get blurred, one's random op-ed spitballing from a newspaper owned by a Russian oligarch, one's talking about a rebel group negotiating for safe passage (six pickup trucks and some ammo - having to include that really helps make my point), and the last is claiming that the US supporting UAE/Saudis means the US is supporting Al Nusra.
