Well, I don't play Europe much because the only real challenge is in beating the local majors which isn't that hard so far because France loves allying every OPM because, you know, diplomats are cool, and trying to expand overseas is a peace of cake. That's my main grip with the game. If I'm Spain, I can just DOW some random OPM native American, land my 100k men, whipe and annex in 1 year (ok, 10k men is just enough, or even 5k but still I could land the 100k so why not?). Then, I just proceed to next tribe and in 10 years, I've annexed all the Americas. Fun? Historical? Neither to me. Historically, Europeans had quality, in some situations definately quantity but they just wouldn't send all their army across the globe and sometimes even weak and insignificant (in EUIV terms) nations could survive.
Also, in the 1600s, native Americans just weren't fighting solely with spears as the game considers they would. Rather, they were supported by Europeans to pull back their Europeans rivals and supported with European weapons, and sometimes even help from European armies (not just in Americas, but in India as well for exemple). That just doesn't happen in the game. If I don't westernize, I get nothing and the static modifier from being in good terms with Europe is insignificant for the poor tech groups. Europe doesn't holds any diplomacy with the locals either but it's Europe VS the rest of the world because, let's face it, it's so easy to conquer them that there's no need to interact with them, and helping them in any way wouldn't help them to pull back the Brits, and diploslots restriction doesn't help.
So, rather than giving historical ways for locals to try to defend against Europe, and forcing historical limits on Europeans (do you think it is realistic to keep Napoleonic squares supplied in China for years? Leave your homeland undefended for a decade and get away with this?), then I think the way how it is represented in the game is still more in favor of Europe than I wish it were. I also which though that such limits were forced on both parties (Europeans and the others), and not to be forced into starting as a small weakling, stick into being a weakling and then turn from weakling to European in a decade and then keep on playing as I were Western tech while my neighbours are the usual pushovers. I just don't want to end up being the American France as the Aztecs, but the game forces me to go that way, not just for an optimal playthrough but rather not to be annexed in a decade.
Long story short, it's either historical both side, or ahistorical both sides, otherwise it's poor gameplay.