Oslo and Stockholm are both about 40min away from city centre. 2.5hrs for both is plenty unless you’re during rush hour which you won’t be. The distance to walk could be somewhat lengthy, particularly at Arlanda but no worse than what you will have in the us. Arn/cph in Oslo tends to be at gates close to security.

But as said, signage is in English everywhere, there’s fast track all airports so you should have 1h45m at each airport at a minimum.