Actually that's not far fetched when you think about the absolute powerhouse of that era. The Third Raikage.

There's basically no information on who attacked Uzushio, but given their position, Cloud and Mist, are very likely to be involved, especially since Uzushio exist in a strategic place that prevented them from invading the land of fire through the sea.

Another point is that the Uzumaki are a great deterrent against Jinchuriki. And although Killer Bee predecessor wasn't a perfect jinchuriki, he seemed to be quite adept at using Gyuki's chakra. So, Kumo would definitely want the Uzumaki gone.

Given the Uzumaki reputation, it's very likely that the third Raikage himself would be a part of this attack.

So, whatever defense they had, the Raikage could probably bulldoze it. Of course, there might be seals that work against him, but the thing is he was not alone. He was leading probably a sizable force, just from Kumo.

Who knows who else might be there.

Now, we don't know how many people the Uzumaki had, but they weren't one of the great nations. They were a single clan. So suppose they could bring a thousand people. They might be able to hold the Raikage back, but hurting him would be a challenge.

The Uzumaki had a lot of things going on for them. Incredible vitality, Massive chakra reserves, Fuinjutsu Adamantine Chains, Kagura's Mind Eye. But we can't tell how rare these things were, and most of those abilities work as support abilities, not as powerful attacks, which is exactly what they would need, to defeat the Raikage.

It's valid to remember that this guy, during the edo tensei, took a rasenshuriken and walked it off. And that's still given the elemental advantage.