I guess I see it differently. You're just beginning what hopefully will be a lifetime of travel, so if it was me I'd use this month as an opportunity to see a bunch of places, admittedly superficially, so that you could decide where to return in the future for more in-depth exploration.

A (Oneworld) RTW ticket with a route something like this would cost around US$4000 starting in Canada ($5500+ starting in the USA) and would allow considerable flexibility, including the ability to travel a little around North America in the months following the RTW trip. (The tickets are good for a year.)

You wouldn't have time for more extensive travel, but for example many of your European destinations can easily be handled in future trips, using trains or cars or low cost European airlines. Instead, you could do a whirlwind trip during which you might discover that some city isn't your cup of tea, so you can remove it from your list, or that some other is so magnetic you can't wait to go back. You have plenty of time.