It depends on what exactly you define as Europeanized (Westernized implies technological acceptance, a la Japan). Also, define European: do you include Turkey in it? Are you defining it as the Indo-European People? Something else?
Many parts of the former colonial empires had some remnants of this; your best bet is to focus on a multiethnic region where a common language would be required to unit the various groups. One region that springs to mind is Southeast Asia; Sarawak OTL existed until it was annexed during WW2; if it hadn't, there is a possibility that it would have existed as an independent kingdom through the 21st century. I'm not sure the languages spoken at independence, but currently the region is nearly half Christian, and is the only Christian plurality state in Malaysia.
However, I'm rather sure that Sarawak's success was its flexibility and adaptability in its treatment of its natives, although I can't give you anymore than that. In any case, it may look more like South Korea or Japan (both being extremely westernized, though still speaking their native language)
Other cases could be other, similar kingdoms/republic in Borneo/the Moluccas/Western Papua; though that doesn't seem likely unless the Netherlands keep them as an overseas department.
Perhaps Gabon if they are kept as a department of France? Same with the Republic of Congo. Cabinda did not desire to be placed together with Angola and could stay with Portugal.
If you include Northern Africa? Italy had a ton of trouble with Tripolitania OTL, but that is the only territory that could potentially have enough immigration to make it distinctly European. Any other choices would be small coastal enclaves (think Ceuta & Melilla).
The Western Sahara was about 30% Spanish when Spain pulled out. It certainly is possible to be kept.
At the fall of the Soviet Union, nearly half of Kazakhstan's population was Russian; a better few centuries for Russia might allow a larger portion of Central Asia to remain under their control.
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Basically, a (but not the only) key thing for any colonial territory to be converted is a lack of a central unitary identity or language. In regions where there is such a prior culture (ex: Korea/Japan), despite the amount of Westernization, they don't adapt a European language as there is an existing linguistic and national identity. Compare that to regions where association is tribal, and a foreign language can easily supplant it and act as a unifying element that is a third party to local interests.
Also, population pressure is important, political realities, general location and ease of access, etc. Despite what Victoria 2 might tell us, just because a low-populated area is brought under an empire's control, it doesn't mean it will automatically become assimilated.