This is going to sound paranoid, obviously, but I was thinking if China ever wanted to start a war with North America, it has quite a sizable population in the US and Canada that could potentially contribute to that aim.
It just doesn't work that way. These people have made their homes here and count themselves as Canadians and Americans. They might have sympathies for the old country (much as many of us in North America do), but the stronger these sympathies are, the less likely we'll go to war in the first place.
There are some interesting articles on the matter:
[1] https://www.nytimes.com/2015/09/23/opinion/whatever-happened...
[2] https://www.economist.com/news/united-states/21642222-americ...
Quite a lot of them are from families that have been American much longer than the PRC has existed.