You can order blackcurrant drinks online, as well as getting extract.

googles

It sounds like the problem was that they could host a fungus that affected other plants, but it's been allowed on a state-by-state basis for some decades after they found a resistant variant.

https://www.grunge.com/879107/heres-why-blackcurrant-was-banned-in-the-us-for-over-50-years/

By the end of the 19th century, farmers noticed that blackcurrants had introduced an invasive species called blister fungus that killed white pine trees, per Business Insider. The fungus solely spreads through blackcurrants rather than from pine tree to pine tree. That means the U.S. was faced with a choice at the time: blackcurrants or the white pine. With national forests highly valued for the timber industry sales used to develop the U.S. as we know it, they chose to protect the white pine.

In the early 20th century, the U.S. government made it illegal to farm blackcurrants and put forth resources to eradicate all Ribes plants from the environment, according to Business Insider. Interestingly, European agriculture met this fungus long ago when it was introduced in blackcurrant plants, but they didn't rely on white pine as fiercely as the U.S., and the "white pine was sacrificed to retain the Ribes," according to "History of White Pine Blister Rust Control: A Personal Account."

Blackcurrants come back

After more than half a century, scientists discovered a new variant of blackcurrant that was resistant to the fungal disease that threatened the white pine. Without the threat to the timber industry, the U.S. government "left it up to the states to lift the ban" blackcurrants in 1966 (via Cornell University). It wasn't until 2003 when New York, where blackcurrants were most heavily produced in the late 19th century, became the first state to uplift the blackcurrant ban in the continental U.S. Since then, some other states like Connecticut and Vermont have also rescinded their bans. But neighboring Massachusetts and Maine (or "The Pine Tree" state) are some of the many other states in which such bans remain (per AHS Gardening, Mass.gov).

The plant itself is, you can get foods made with it.

They are now legal to grow in many states. Unfortunately still not going to find it in a grocery store most likely. I grow my own in the backyard so I can have some at least part of the year. They're perennial, very easy to grow, and produce a ton of berries. Gooseberries were banned for similar reasons, but are now also legal in many states.

And cloudberries! I want to taste cloudberries!

Gooseberries grow like crazy in Colorado, every other garden around here has at least one bush. Never seen them at a grocer though.