The Oxford English Dictionary has a significant entry on the various uses of colonial. Sense 1b relates exactly to the American meaning of "from the colonial era".
1b. Belonging to, or characteristic of, the period of the colonies,
esp. of architecture or furniture. North American.
1886 Harper's Mag. Oct. 668/1 The building has rather a colonial
character with its long corridors and pillared piazzas.
1892 R. Kipling Lett. of Trav. (1920) 21 The Colonial craze, which
means white paint and fluted pillars.
1939 A. Toynbee Study of Hist. VI. 60 The Americans use the term
‘Colonial’ for the eighteenth-century style of architecture which the
English call ‘Georgian’.
1968 Globe & Mail (Toronto) 13 Feb. 30/5 (advt.) Custom built
Colonial home, five charming bedrooms on second floor.
There is a single, brief, entry in the OED for a verb colonialize albeit, described as an "isolated use".
transitive. To make colonial. Apparently an isolated use. 1864 E. A.
Murray Ella Norman I. 190 If you remain here, in a few years you
will be colonialized.
The fact that it is spelled with a Z suggests it is of American origin.
The meaning "to make colonial" is vague. But it would seem perfectly reasonable to use colonialize for the sense you describe.
There is no entry for colonialized but if it exists as verb it must have a past participle, and past tense.