To try to do so between 1/1/1900 and now will be extraordinarily challenging, it doesn't seem very plausible... short of it occuring because of extraordinarily disaster befalling the US and/or UK.
If you want to move your thread to Future history, though, who knows

The rapidly-worsening climate warming will ultimately be most beneficial to Canada and Russia, all things considered, and I assume the population growth will ultimately be pretty crazy as a result. Canada is more open to immigration and better tooled to deal with it than Russia and definitely has room to grow north, so its not a total stretch to believe that within a century, it could experience a boom reminiscent of the conquest of the west for the US, if a bit more chilly, while the US suffers from catastrophic natural disasters and desertification.