There are many cases which you could use for this discussion. Currently United Kingdom is leaving European Union (since 2016 the topic is on). But you can also use other examples.
*As the United Nations. Indonesia left the organization in 1965, but later re-joined the organization in 1966.
* European Union- Had few territories that left it. Greenland in 1985; Saint Barthélemey Island in 2012 and French Algeria in 1962.
* Mercosur - Venezuela was withdraw from Mercosur in 2016, not by its own will, but by the organization decisions.
You can choose one of these cases and research, what were the advantages and disadvantages, and opt accordingly with your values if is best to support or not the decision of the nation to withdraw the organization.
The reasons to withdraw is sometimes related to tax payments, desiree for political independence, being unable to comply with the organization rules or changes of interest and policies.
Using as an example for this discussion of a nation that is leaving an organization the case of United Kingdom leaving European Union you could choose to support that decision of United Kingdom to withdrawal from the European Union. The reasons for the stance on this issue is that UK already has a different currency, instead of Euro works with Libra as well. Also British pays a lot of taxes for European Union, it is the second country that contribute more for the organization and this would revert this taxes for UK. Beside these European regulations affect UK laws and power of decision in some matters related to business and immigration issues, to withdraw means more freedom to legislate. Lastly UK could give more support for local and national companies, with according with EU organization application of the funds has to pass through EU board and regulations.