The 1993-1995 U.S. expansion period provided some of the CFL's funniest stories, and the expansion fees brought in during that era may have helped the league's Canadian teams survive, but the foray into the United States was a disaster from a business perspective. Now, it seems that some fans in St. Louis are reacting to the loss of their NFL team by trying to recreate the CFL USA era, launching a STLRAMSCFL.com website "to spark the conversation and promote the concept of bringing a CFL expansion team to the city of St. Louis" and suggesting that there "are many great football towns in the US that still don't have a team" and could make up other U.S. markets for CFL expansion, including Milwaukee, Orlando, Portland and Memphis. This is an entertaining idea, and it's nice that Americans are noticing the CFL, but this plan is incredibly flawed and is never going to happen under the current circumstances.
Yes, the CFL has a strong argument as the best professional football league in the world outside the NFL, but that doesn't mean expanding it into the United States again makes any sense. For one thing, American professional leagues apart from the NFL have next to no history of success: from the USFL to the World League of American Football to the XFL to the UFL, there have been plenty of massive failures, and even arena football (which has a better case as a spring league with different rules that doesn't go head-to-head with the NFL, and has managed to hang on relatively consistently in one form or another) has faced major struggles. Running a non-NFL professional football league in the U.S. has generally been a disaster ever since the NFL-AFL merger in 1969, and it looks like a worse idea now than it's ever been thanks to the NFL's dominance. Consider the suggested markets, too; Milwaukee is thoroughly Packers territory, Orlando was a CFL USA expansion that never even got off the ground, and the CFL USA Memphis Mad Dogs lasted just one season with just over 14,000 fans in attendance on average.
Even if the CFL did go to just St. Louis, and was somehow able to recapture the success of the one CFL USA team that did work (the Baltimore CFLers/Stallions, who were both a great team and managed to find love in a city disappointed by the Colts' exit; that's much more unlikely in 2016 given the NFL's increased dominance and the other nearby teams), it likely wouldn't work out in the long run. Fans might come for a year or two as a protest against the NFL or from curiousity about the CFL, but they'd be unlikely to demonstrate continued interest in a foreign league with different rules. If by some chance they did, that might not end well, either; consider that the Stallions' success helped the NFL return to Baltimore, forcing them to relocate to Montreal. (Also, the use of "Saint Louis Rams" is funny: first, it's St. Louis, not Saint Louis, and second, the legal injunction the NFL took out against the Baltimore team, initially the "Baltimore CFL Colts," shows how they won't let anyone else use their team names.)
Beyond the above reasons why no one would likely want to own an American CFL franchise, the CFL itself has no need to go to the U.S. again. For one thing, there's not a lot to gain by doing so; expansion in Canada is difficult enough, as we've seen in the discussions around Atlantic Canada and Quebec City, and U.S. expansion carries far more perils with less potential upside. The CFL is also in a much better situation now than it was during the CFL USA era; the league's TV contract and very-favourable-to-the-owners CBA mean it's on solid ground, so there's no need to go chasing quick cash in the form of expansion fees the way the CFL did in the early 90s. The CFL expanding to the U.S. again would also threaten the league's relationship with the NFL (which is generally healthy right now) and make it easier for that league to expand to Canada at a future date if they so chose (which is problematic for the CFL), and it would damage the CFL's Canada-centric marketing and their teams' requests for government funding for stadiums. So, there are a ton of downsides to the league trying to go to the U.S. again, and next to nothing to gain. Sorry, St. Louis, but the CFL won't be meeting you there.