Strange that no-one addresses your globules, but seem to know everything about US-05 and starters...
I can't see from the picture what they are. They're probably just yeast clumps. Did you use a stirrer or just swirling?
Yes, you can make starters from dry yeast. It is usually
a) not needed as the yeast count is typically high already, or
b) not recommended since rehydrated yeast is ready to go, or
c) just as easy and cheap to pitch a 2nd pouch.
But the point is, you could, just like any other yeast, and when in doubt of its viability (e.g., outdated, improperly stored), this is a good sanity test for it.
That said, the yeast is also ready to go to make you a (huge) starter. If it multiplies in a fermentor of wort/beer it will grow in a flask with starter wort too. Yeast is yeast.