After WWII is going to be tough...could it be perhaps a bit earlier?
IIRC in OTL the Guyanas were tossed out as a potential location for a refuge for German/Austrian Jews fleeing Nazi Germany. In OTL the idea fizzled due to various factors, but let's say for the sake of argument that someone/something backs the idea and gets busy ASAP. Basically under this scenario, everything that did go wrong for the emigration of Germanic Jewry in OTL goes right. Within months of the conference Thousands of Germanic Jews are headed on boats to French, Dutch, and British Guyana which now find themselves under a joint immigration board. There the Jewish refugees find themselves put to work on farms and other infrastructure projects, financed heavily by the JDC.
Come WWII an agreement is made in which Jewish immigrants from Germany to the Guyanas are unable to leave the country due to the possibility that they might be German spies (as opposed to OTL where the Allies simply refused them entry/interned them on the same grounds). Despite these restrictions, thousands more Jewish and other refugees pour into the Guyanas where they continue to work and participate in the war effort. The presence of Jewish refugees in French Guiana is enough to convince that colony to side with De Gaulle, and soon enough thousands of young Jewish men have signed up for the Free French Foreign Legion. As WWII progresses the Guyanas continue to grow closer economically and politically due to improved infrastructure, wartime cooperation, and the large population of Jewish refugees in all three countries. When the war ends, around a million Jews are living in the Guyanas and have founded thriving communities in addition to contributing heavily to the economy and culture of all three Guyanas.
In TTL with the presence of a successful Territorialist (non-Zionist) Jewish settlement that movement is less discredited and surely many Jewish refugees will choose Guyana over the embattled nascent state of Israel. For the sake of the scenario let's then assume that the lower Israeli population leads to that state's destruction at the hands of the Arabs and a wholesale flight of the Jewish population to settlements in Guyana/the USA.
In the 1950's the integrated Jewish populations of the Guyanas along with the local populations, vote for independence and Union, creating the Guyanan Confederation which soon grows to become one of the world's strongest economies.