That’s a bit emphatic, surely?

If you can make a B2 bomber stealthy then perhaps you can do the same with a balloon - the bags are thin polythene [1] and I assume you could combine geometry and radar absorbing material to make a payload disappear.

If it were that obviously visible why wasn’t it intercepted when it crossed into America’s air defence identification zone?

[1] https://www.nasa.gov/scientific-balloons/types-of-balloons

It's very clearly not stealthy, it's got solar panels hanging from it. I'm sure you could make a stealthy box, but this is not that.

If you don't know what your talking about it's usually more polite to admit it, instead of trying to double down.