Let's see here. There's a LOT of big-medium sized shows within a 10 hour drive of Toronto.
Ohio Renaissance Festival - just outside of Columbus/Dayton - about 8 hours from Downtown
Michigan Renfest - just outside of Flint, MI - about 4 hours from Downtown
Connecticut Renfest - just outside Hartford - About 10 hours
Great Lakes Renfest - Ashtabula, Oh, about 6-7 hours around the lake
*Pennsylvania Renfest - about 10 hours but Worth It
*Bristol Renfest closer to 12 hours Just north of Chicago DEF worth it
I starred the biggest of the shows that are further away but WELL worth visiting if you really want a great Faire experience. I can tell you this cuz I've worked all those shows (laugh) and those two are the most impressive.
The Biggest of the Big - Maryland or Texas I would recommend flying to; even the Bristol show. You can still fly fairly cheap on Southwest out of Buffalo/Detroit; and it's easy to shuttle to those airports & parking is also fairly cheap.
Hope this helps; enjoy whatever faire you choose!
Best,
Bunnie
The Limeybirds