The national / federal government is able to send agents and enforce its will on states / provinces. Israel was not able to send anyone into Gaza.
It would be a "breakaway province" situation, except that:
a. Israel intentionally got all its citizens out of that place and
b. Israel had no intention of taking control and forcing Gaza to join back into Israel.
Israel mistakenly thought Hamas was transforming into a national government that is busy governing its territory.
Gaza was mostly an independent country at war with Israel and not even a little bit an autonomous province of Israel. The war could not be resolved and so it was stuck in a state where Israel thought it prevented Hamas from bringing in heavy weapons but did not want to commit to conquering a city.
I think some people thought that after Israel pulled out in 2005, and Gaza became autonomous, it would become a normal independent country, and people still treat Gaza of 2023 as if it's the Gaza of 2005.