The news of people releasing fish brings light to a very loud minority. Very few people actually release their fish, and when you do you only hear about it because they happened to release a species that does well in our environment. You hear about Florida a lot because Florida is pretty much the only state where nearly all the tropical species we get can survive perennially, thus creating tons of little populations of invasive species. Even then not everything thrives or reproduces, there is a list of species reported from across Florida where it can be seen that at least a third of the invasive species reported never take hold and die off. This is just Southeast asian, west african, and south/central american species by the way. Even giant snakeheads are occasionally reported in florida but no reproduction is ever recorded. Everywhere else in the united states it gets too cold in the winter for most fish to survive. Even the only US native cichlid (herichthys cyanoguttatus) can't really take hold north of texas.
I personally have only encountered three released fish over my lifetime, that being a full sized bala shark I saw in the lake I've fished for the last 15 years (saw once, never saw it again), and two cichlids in a neighborhood pond, one being a vieja/amatitlania amphilophus hybrid, the other being a full sized albino oscar. Oscar died in the pond once it got cold, the hybrid my friend wanted so I caught it out but it jumped in my care. Not trying to justify releasing aquarium fish, but just saying it doesn't happen very often, and isn't as detrimental as it's made out to be.
The only other place I know large populations of invasive species exist is in and around Utah, as there are lakes full of Malawi cichlids, though those only exist because they are heated by nearby factories and thus would not be able to expand into natural environments. Warm runoff from factories also produces small streams that support small populations of livebearers scattered around the country, but again these are few and far between and closed ecosystems.
The problem gets a bit more confusing with Chinese species, as the climate of China is perhaps the most similar to that of most of the US. As we've seen with northern snakeheads (the only snakehead that has taken hold north of Florida), silver/bighead carp, and in some places goldfish and dojo loaches, they are able to take hold because they naturally come from a place that has a similar climate to us. However, these potentially detrimental species are already taken into account, and there are legal limitations to owning most of them already. Thus in regards to the fear of releasing exotic species of fish in fear of invasive populations arising, this should not be considered a valid argument.
As for concerns of conservation, freshwater species collected in large numbers for the aquarium trade are collected sustainably, I'll see if I can find the documentary on one of the south american villages that maintains and protects a population of neon tetras for the aquarium trade. It's a good example of the contrast between freshwater and saltwater collection methods. Admittedly saltwater collection is a bit more intrusive, especially when it isn't for specific private collections, though I feel by that logic a ban should not be necessary per say, rather permits or something along those lines for those determined enough to want wild caught fish for their collections. Going back to freshwater however, collection and moving fish into the hobby has a sort of adverse effect, as it maintains a population of hundreds of species that are naturally losing their habitats. Most central american species have at least some sort of threatened conservation status because of habitat loss. Endlers are a good representative of south american species, because in spite of their abundance in the hobby they are thought to possibly be extinct in the wild. This logic applies to a multitude of fish on the other side of the world as well. Banning their importation outright for the purpose of conservation would ironically be more detrimental than their collection. At this point it becomes less of an issue of how many we take out of the environment, and more how many are still in existence, when they no longer have an environment to protect.
That's just fish though. Bird, reptile, and amphibian importation is already heavily regulated, and in regards to them taking hold in the US, again, most can only survive in select states like Florida or Texas year round. As for insects, insects also apply more to the latter. Most insects imported as feeders or pets usually can't even survive in a house once escaped.
Hope this helps clear things up, and adds another perspective to things.
