Obadiah is about Edom’s sin,…

Obadiah is about Edom’s sin, not a standing rule that every nation (or Christian) must give unconditional political backing to whatever a modern day government, that happens to call themselves "Israel", does. In the New Testament, the “Abraham blessing” is fulfilled in Christ, and the family of Abraham is defined by union with Christ, not ethnicity or geopolitics:

“Now to Abraham and his seed were the promises made… And to thy seed, which is Christ.” (Galatians 3:16, KJV)

“And if ye be Christ’s, then are ye Abraham’s seed, and heirs according to the promise.” (Galatians 3:29, KJV)

The curse that matters most is dealt with at the cross: “Christ hath redeemed us from the curse of the law, being made a curse for us…” (Galatians 3:13, KJV)