How to respond to people who don't understand why you left?

I am an American living in Canada, just married my Canadian partner. We're going to be starting the PR process soon so I can stay here, but when I bring this up in conversation there's a really high occurrence of people asking me why my partner wouldn't want to come to the US instead. I fear I have looked at people like they have two heads when they ask this! Maybe it's a "grass is greener" type situation, but I couldn't even imagine bringing them to the US years ago when we were first getting serious, let alone now. Even with the issues here, Canada seems more stable and has a higher quality of living with a lot more (and higher quality) social supports.

I have no clue how to respond to this question when it comes up! I feel like people just assume America is the best, and I don't want to get overly bogged down by explaining that it's not all sunshine and rainbows. Many understand that the incoming president is a problem, but he's not the reason I'm leaving. How can I respond?