Treaties can be renegotiated, they can be obsoleted. Backing out doesn't necessitate wrong doing. But my point of course is that men aren't angels, and as such we all sign contacts, borrow money, form partnerships, etc. none of which are done on handshake deals, and often times collaterals are collected, liens are imposed, etc, because men cannot be trusted. World leaders, in an arena where the stakes are hugely higher, cannot be and are not trusted. We even spy on our friends remember. So yes, the notion that we "trust" our friends and allies deserves that emoticon.
Trust but verify. Note that a signature or handshake is not verification.
When we ignored the Syrian civil war and abandoned the Iraqi army we did everything necessary to allow ISIS to prosper. I am being kind when I chalk it up to abject stupidity on the part of the White House.
I have no problem with our ignoring the Syrian Civil War. The Anti-Assad "rebels' " allegiences were questionable at best.
I do however have a problem with how Obama handled Iraq. That twit let ISIS continue to take territory and didn't do squat until that American journalist was killed.